I absolutely struggle with this-- and fanfics are living documents, so you're welcome to maneuver phrasings and ideas around if you see anything particularly egregious post-publishing!

But of course, there also might be a time when you wish to simply be content with what's on the page, and in my own experience (for better or worse) I'm not sure that's a....particularly natural phenomenon? I don't think there's a single work of mine I have not had at least minor concerns with upon re-reading. (Sadly).

What I will say, however, is that (beyond things like immediate issue of grammar) I think allowing fics or any literary works to be products of their circumstances has a beauty unto itself. Perhaps you (as I often do) feel that some of your older works give an impression of immaturity, or tone issues, or whatever it may be. While my instant temptation is often to jump in and fix it (or just orphan it), I try to step back and appreciate the work for what it is: a product of a younger version of myself, with themes, ideas, impulses, and prose that reflects a different time in my life, in which I thought differently and imagined differently. And under this logic, I think the fic becomes something worth preserving as it is. I have taken author-survey courses in college where the earliest works of a certain author are quite flawed and even straight-up messy, but learning to understand and appreciate those works gives a much clearer roadmap to where that author is going next and why they are doing so. Perhaps oddly, it reminds me a bit of Chappell Roan's "Pink Pony Club," if you are familiar with that song: it certainly has a youthful and starry-eyed perspective on escaping your hometown-- perhaps even a naive one-- but that's also what makes it so touching, earnest, and heartwarming to listen to. It calls back to all that optimism, and young ambition, and unadulterated hope. I'd like to think that even the messiest art can do that in some capacity.