Take your eyes off the plot. Focus on originality in your characters and setting.
I'm not saying this is easier, it isn't always easy to create new characters and new character dynamics, but this approach can work to create interesting plots simply because the plots are "natural" outcomes, not pre-engineered to look like something else.
It is true there are a limited number of plots, various works classify them in anywhere from three to thirty six basic plots.
Three, Six or 36: How many basic plots are there in all the stories ever written?
The Thirty Six Dramatic Situations
The Seven Basic Plots
The 20 Master Plots and How to Build Them (by Ronald Tobias).
They can all be valid; the number depends on how much detail about the plot one takes into consideration. (The more we generalize the plot, the fewer plots there are.) Regardless of the exact number, there are really not very many plots considering the million stories they claim to cover.
However, for your problem, I think it is important to point out something important about these analyses: They are all after-the-fact. Good stories existed long before anybody tried to classify their plots and develop point by point outlines of them.
The reason that is important is because it proves the plot is an artifact, a side effect of just telling a good story. The original authors of these plots did not follow any guideline, they sat down to tell a good story and entertain or educate people that way, and it so happens that enjoyable stories tend to share certain kinds of common structure. It is built into the typical human psychology, somehow, that (for example) the "try-fail, try-fail, try-win" structure in a story resonates with us; or that (post-childhood) we don't care much for stories that are an uninterrupted series of successes for a hero (wish fulfillment stories).
Why is that? You will notice most of the plot elements match life experiences, metaphorically or allegorically, for typical people. Troubles with evil, or romance, or taking on adult responsibilities, dealing with disaster in health, or nature, or accident. Finding justice, protecting your family from predators (animal or human), finding safety and prosperity, navigating sexual maturity, becoming an independent adult, becoming a parent. Dealing with corruption or tragedy.
Why is that important, that plots are characterized after the fact?
It means that good stories will naturally fall into one of these categorized plots. So you don't really have to plot in advance to tell a good story, just like the originators of all these plots did not follow any guideline.
Instead, find a favorite you understand, whether it is 7 or 20 or 36 plots. But put it aside; this is a reference work for later, it is not a planning document!
Instead, think of the ONE plot: A hero has a big problem to solve.
A mother with a sick child that doctors have given up on. A soldier uncovers deep corruption in his own government. A girl gets accidentally pregnant. A spy is ordered to kill a man he knows is innocent, and doesn't want to do it, but if he doesn't a fellow spy will and that isn't acceptable either.
The next thing to understand is the Three Act Structure of a story; again this is another after-the-fact analysis of how good stories work, not an iron framework to follow. So consider it a generalization of a million good stories and not something you have to follow religiously; not every good story does. What follows is a pretty detailed reference that is useful, it tells you to plan your story using the three act structure, you can take that advice or just use this later as a reference, to see how your story is turning out.
How To Plan Your Novel Using The Three-Act Structure.
As a discovery writer, I discover my characters and stories by writing about them. Not in the "questionnaire" style, or listing a bunch of traits, I write actual prose, dialogue, and scenes. I present small day-to-day problems for my character(s) and see how they would solve them. This is not intended for publication, but to help me find the voice and personality of how my characters work.
I know the beginning of the story should open on the hero's "normal world" before they meet their "big problem to solve", so that is how I begin. No big problem, some small problem she has to solve; e.g. she woke up, there has been a power failure, she is late to work and has no frikkin' lights or electricity to get ready for it.
Make your character's personality original, not a copy of any other hero you have read, and if you feel yourself writing some hero you know then back up and change your hero. Think of something else.
Do the same for your setting. Recognize clichés and break them; if you can't break them (i.e. you need FTL) then use them without fanfare or explanation at all, don't make them part of the PLOT. e.g. There is FTL, we use wormholes, with no backstory. Not how they were discovered, or by whom, we don't explain wormholes any more than we'd explain horses or who invented wagons in an old west story. I don't think Star Wars ever explains FTL.
If you feel forced to use a setting cliché then use it casually without celebration, take it for granted, as you'd use guns, horses, wagons, sheriffs and saloons in an old west story. I've never seen an old west story in which they try to ground the audience with a story about who invented the saloon or the rifle or the stirrup. Treat SciFi clichés in the same way.
Still, do try to make as much of your settings as possible original with you, and try to give your characters non-stock personalities, a mix of likes and dislikes that don't have to be over-the-top but aren't immediately reminiscent of Gandalf, Han Solo, Jason Bourne, 007, or any other famous character.
That is how you arrive at a unique story even if your plot will (inevitably if you find a good story) kind of fall into one of the standard plots.
My approach is to NOT plot, exactly. I start with a big problem. Maybe there is a villain, maybe not. I have an idea of how this story could end, often a standard ending: e.g. She defeats the villain in battle. But once I have a mental model of my character, I roughly follow the three act structure, introduce the problem, and (while making nothing easy for my hero) I try to think of what she would do, and let her take that path, scene after scene.
As Stephen King says, if you keep advancing the character and don't let her stall out, the story has to come out somewhere. As an author, don't make choices or write scenes in which nothing changes. If a reader could just skip that scene, and learn nothing about the characters, setting, or problems to be solved, get rid of it. Every scene must step to somewhere different, internally or externally. Obviously if the character succeeds at something, that is an advance. But if they fail (as they should), that should produce an advance in their understanding of the problem, it should narrow the range of possible solutions.
If you do that often enough, the story must arrive at some destination, you cannot let the failures go on forever or readers will get bored. if the hero's understanding is increasing, and the options are narrowing, they will finally come together and you have begun Act III.
(If along the way, your characters most likely decision will preclude the ending you have in mind, find a better ending that is not precluded (3 out of 4 times I can); or undo the decision so your ending is not precluded. Don't keep writing without some not too vague idea of how it can end.)
Then analyze your story.
Now is the time to break out those references. How well does your story fit into the three act structure? Start tweaking it until it does; that is what good stories look like. Delete stuff, add stuff, follow the percentages (see below, to meet word counts per plot event in the Three Act structure).
Which of the "standard" plots is most like your story? Figure it out, go through your plot points. Are you missing something the standard plot has? Is it necessary? Can you fit it in, would it make your story stronger? You don't have to change it, I just want you to make an informed decision. These standard plots are a distillation of what good stories look like, but it doesn't mean every good story contains each and every element of that distillation.
And that is the final thing to know about stories. There are thousands of books in each and every one of those standard plots. Obviously with so many, all following the same plot, if we sort them by how much readers love them, there are going to really good stories on top and really bad stories on the bottom, all using the same exact plot!
What makes your story good or bad isn't the plot, but how well you immerse the audience in your characters and setting, and the imagination you can put into making them and the obstacles they face original. For example, when Luke battles the wampa on the ice planet Hoth, nothing is original about the plot points of that encounter. But the setting, the characters of Luke and the monster, the light saber, using the Force to get it, the TuanTuan he rides, are all original, making that encounter, battle and resolution all fresh story.
Your "creative plot" will arise naturally out of creative characters and settings, those will produce both fresh problems and fresh solutions we haven't seen before. If you avoid the clichés in the setup, you will avoid the clichés in the resolution. Of course with enough generalization you will, like all good stories, fit into one of the standard plots, but it won't seem like it and that alone will not give away enough to the reader for them to be bored. They will want to see how your hero solves this problem.
By analogy, every time we watch a RomCom we know the boy and girl get together. But we watch to see how this boy and this girl get together.
Edit: Following the percentages.
Added in response to comments. If you look at the three act structure (especially as applied to movies), in the link I provided, they suggest 27 chapters; 9 chapters per Act, in three blocks of three. If the chapters are of equal length, then each chapter is 3.7% of the total. I do not work to fractions of a percent, I roughly work in chapters of 5%-10% of the total, and end up with something in the teens for total chapters. Which is roughly what I see in other novels.
Nevertheless, the ideas are the same:
- Block One (of 9 blocks) – Introduce Hero in Ordinary World
- Ch 1 Introduce Hero in her Normal Word
- Ch 2 Inciting Incident
- Ch 3 Immediate Resolution
Of nine equal length blocks, this first block is 11.1% of the story. I expect about the first 10% of a book will introduce my character in her normal world, without any hint of the big problem, but I do give her some "throwaway" problems to solve just to provide some conflict and give me a chance to build her character and the setting; the nature of the world she lives in. It has magic or does not, it's medieval or modern or futuristic, I want to show what kinds of morality, religion, politics and resources are available; not just hers but what she must deal with. In this block, she will also encounter some inciting incident (read from the link). eventually (in block 2) this is going to disrupt her life and plans. By the END of ACT I (for me in the 25%-30% range), she will leave "the normal world" (physically or mentally or both) in order to solve her big problem.
I kind of write to these percentages by instinct. I don't worry while I am writing if I am going long or running short, I just write. I don't know how long the book IS yet, so I am unconstrained. But when I try to fit my finished story into the Three Act Structure, I let that guide me on what pieces are too flabby, and what pieces are too skinny: I want to hit the points at roughly the right time, give or take a few percent. So if I finished at 400 pages (at 250 words per page in submission format, so 100,000 words), the first block (above) should be 10% IMO, 40 pages, 10,000 words. I will go through and clean it up several times, but if it is running 55 pages, I know on the first pass I need to cut hard and tighten it up. If it is running 25 pages, I need to see if it is too skinny and can be fattened up, probably with a whole new scene, but perhaps I can find a way to do more world-building, ore create a richer setting, or find a scene that reveals more character.
In the end I don't much care if my novel is 90,000 or 130,000 words. It takes what it takes! But after writing I do tend to push my stories in the direction of what a good story looks like, both in the Three Act Structure, and in terms of the standard plots, because I find these tend to make the stories stronger.
As you can tell from this post, I have a tendency to overwrite and have to condense; but as a saving grace, I can be pretty ruthless with cutting my own writing! I've always thought it is better to write six hundred pages and sell three hundred, than to write three hundred and not sell any. Perhaps because it is fun for me to write scenes, and my fun is not diminished if something I wrote is cut because it wasn't necessary, or was repetitive, or just didn't fit right. So I don't mind "experimental" scenes and wandering about on a tangent and having to back up and discard something.