I said in an earlier post that it's okay to wait to write a story. But … I think I should expand on that, because I also think that, in most cases once you start writing that first draft, you should not take years to write the story without understanding one important thing:
If it didn't change, then it would not take years to write. But, the longer you fiddle and mess with the story, the more it will change from your initial idea. This is perfectly fine (that's why it's called editing), but I don't think many people are prepared for why their idea might change, and so, they continue fiddling with it, knowing something needs a change without being able to put a finger on it.
Especially when you're a teen, you're developing two senses: Your objective understanding and your subjective taste. The latter is going to change throughout your entire life and will be especially inconsistent when you're young. Your "objective" understanding is your understanding of what is socially considered "quality" writing. E.g., it'll be your understanding of how character arcs work, what are "good" plots, how dialogue flows in an entertaining manner, what make for "satisfying" endings, and etc. These are your foundational opinions. I'm calling them "objective" because they're unlikely to change and are likely to be socially agreed upon to be the cornerstones of what makes a good story.
When you're a new writer, you'll be learning how to employ your objective knowledge and put it into your writing. When you're a teen writer, you'll also be developing your objective understanding, hence why you'll be especially critical of your own work. You're going through an extreme learning curve. You're learning so quickly that your ability to critique is stronger than your ability to write. So, obviously, your story will change, and these are the changes that should be encouraged.
Eventually, the curve will flatten and your ability to merge your objective understanding with your writing will blossom. But, even then, you still have to deal with your subjective taste.
In my earlier post, I said that it's okay to wait because you know you're not ready for a story. It some cases, this means you're able to predict the ebb and flow of your own taste, which is awesome, but it often isn't nearly as predictable.
Taste is … subjective. Taste is the specific type of character arc you want to write, the type of plot that you favor, the type of entertaining dialogue you enjoy writing, and the kind of ending that is satisfying. One year you may prefer heartwarming stories and another year you may prefer tragedies.
This brings me back to my original point.
If you write a story over the course of ten years, your subjective opinion will change. Your idea of what you want will change, despite that it may not necessarily change the objective quality of the story.
Have you considered that all those little edits, shuffling character arcs around and whatnot, do not actually change the quality of the story, but merely changes it to what you consider subjectively good at the moment?
The writing community loves reminding you that you're not alone in disliking your own writing, but no one seems to mention that the reason you hate it (and your friends love it) has nothing to do with the quality of the story but with the fact that your vision of the story changed while you were writing it. Your original idea does not match what you wrote, and you confuse this with thinking that you wrote it wrong.
It is often the case that your subjective taste changed and you didn't even notice.
So, when you're editing and rewriting that blasted novel you've been working on since forever, consider that maybe the problem isn't that you wrote a bad story, it's just that you changed, your story changed, and it's time to write a new story which fits your new tastes.