Sometimes the changes I think of making to my story aren't better or worse than what I already have. It's just preference. And I have to wonder, do I really prefer one over the other?
I think on a subconscious level, I wanted to explore every possibility, every unturned stone, and then pick what was best out of all of them. But with so many characters, complexities, mysteries, relationships, themes, and opportunities for worldbuilding, it's unrealistic to do that. And once the story reaches a certain point, it's not a better or worse option anymore, it's just a different option. Often it becomes an exchange. If I switch this, I can gain this and that, but lose this and that. Sometimes it's not.
There's a saying for movie-makers: "A movie is never finished, only abandoned," meaning, one can always do more work on it. He just finds a good spot to stop.