True or false: No author has ever or will ever get their first novel published?
I don't know. I did a quick search and didn't come up with good results. However, I do know that sentences containing nobody, everybody, never, and always are as a rule false.
They are too general and the fact that we usually use such sentences to push ourselves or others down not only makes them false but harmful as well.
Maybe there is an author out there that was published on their first try? Maybe someone will in the future?
In this day and age, you can definitely publish your first novel. No one might read it. And you should probably not use your favorite pseudonym... But you can publish it...
If you don't go all in, it will take longer to get good enough
Reasoning about when people get published and such risks raising thoughts about hacking the system by taking it easy on the initial novel or novels.
It's a bit like the joke about heartbeats: You get a limited number in a lifetime so you'd better not exert yourself or they'll run out too fast...
Not going all-in on your novel will likely prolong the time it will take you to become a good writer. You'll miss important lessons or you'll get them in smaller portions over a longer time.
Not going all in ever is, in my opinion, a recipe for never becoming an author. Or for that matter published. (Agents and publishers will know if you went all-in or not...)
My advice is to go all-in from book one and keep going.
After all, if you decide to self-publish your first novel and someone actually does pick it up and read it, what do you want them to read? The best you had at that time or something you kinda wrote?
You can pick it up later and finish it
Nothing prevents you from taking your best idea, fail writing it, put it aside, and pick it back up later.
Sure, you might get published and later in life realize that it was a poorly executed novel.
Or you might start in one genre and then realize another genre is a better fit for you. You might still reuse parts of the first novel, or have them floating around in your mind as you write other novels.
It may also be that your first novel follows a theme all your novels will follow, that you'll actually spend your career exploring a single theme or a single type of story from many different perspectives. It could happen that the first novel, published or not, will just be one instance of that exploration.
Writing is a lifestyle
Is writing for you? I don't know. I do think, however, that if you write your first book as if it is obvious that it will get published you'll be able to figure out much faster if writing is for you or not.
I suggest that when you write you mean business, you write to get published, you go all-in and produce the best you can, using the best ideas you have. You do it professionally as if it was a job. You start it, do it and finish it. With deadlines, if it helps you from spending a decade "going all-in"...
Otherwise, you will spend your time trying to write instead of actually doing it. (You do, or you don't, there is no try, as it so wisely has been said...)