a writer does not have to worry about looking for a "great idea" for a story, but simply focus on taking fairly interesting story ideas and making them as enjoyable to read as possible. Is that correct?
That is almost correct; but the question as phrased has hidden caveats.
For one, "a fairly interesting story idea" made "enjoyable to read" is what we call a great story!
Which almost makes this a tautology; e.g. "The way to write a great story is to write a great story." But not quite; the hidden definition saves it. So yes, find a fairly interesting story idea. Make it enjoyable to read. That is one way to create a great story.
As Mark Baker notes, humanity has already derived and distilled the outlines of great stories, basically all patterns of conflict, setbacks or failure, actions taken to overcome failure that succeed.
That is the essence of "story" and how we inherently choose to imagine our lives. Things stand in our way and we overcome them; whether we are saving the world or inventing a new recipe for cookies, saving our child from disease or trying to navigate law school, or wizardry school. Even if we want a house instead of an apartment, and we take steps to make that happen.
Picking one of those GREAT general plot outlines is one way of making something "enjoyable to read". Note these were never dictated, the great outlines became great millennia before the stories that adhered to them were analyzed and categorized. Consider them observed phenomena; they are the greats because they fit the pre-existing human psyche we evolved from our hunter-gatherer days before even farming existed; the stories of heroes told around campfires fifty thousand years ago, the stories themselves evolved by retellings over thousands of years into the essence of what makes a story great.
by describing the plots in greater or lesser detail, you can arrive at more or fewer number of great plots, anywhere from two to 32, perhaps even more with more detail. The number doesn't matter, all of them are reflections of the common human psyche and our need for instruction by example in how to achieve success in life and deal with defeat or failure.
Part of making a story "enjoyable to read" is the author inventing something new for the story, new plot twists, new characters, new kinds of problems to solve. Most (not all) romantic comedies follow a strict formula, but the characters are new, the jokes are new, the settings are sometimes new. The same goes for fantasy, mystery and scifi, or mashups of these.
So your "fairly interesting story idea" will still require a lot of imagination to be "enjoyable to read", it must have enough "new" stuff so that the reader is not bored and certain they know the ending.
Poetic words alone will not carry the story. The reason is simple, in order to be "enjoyable to read", the reader must always be reading to find out what happens next; like in the next ten pages or so.
Part of that is wondering how a conflict will turn out; part is interest in the character(s), the world-building, the little and big problems to be solved. Part of life is learning to navigate new environments or situations, social or physical, and your characters should be dealing with those.
Fortunately, we can take a "fairly interesting story idea" and, through brain-racking work, invent enough "new stuff" to show along the way to make that whole novel/movie compelling and fun. To pack in a variety of problems/challenges/puzzles/battles for the hero that the reader wants to follow them and see how they prevail, or fail and recover.
No matter how well your words land on the page, if the reader gets bored reading, stops wondering what will happen and stops caring whether the characters win or lose, the story will not succeed, even if it was a fairly interesting premise. You must sustain some kind of tension for unanswered questions throughout, including the biggest "finale" unanswered question, for this to be "enjoyable reading".