I post occasionally on Archive of our Own and have done their Yuletide thing a few times.
I used to be in a fandom but it was really cliquey. Certain writers had loads of kudos no matter what and what had started out as a pretty free fandom became centred on them. They became a bit like celebs. Anyway, I'd had an idea for a story and was formulating it when I heard that one of the Chosen Writers was planning a story with the same premise. I got mine finished and started posting it up, but not under my usual name.
One of the comments I got went something like this: OMG! OMG! Chosen Writer this was AMAAAZING!! Etc etc.
It finished with: If you're not Chosen Writer, then well done, it's not a bad start.
Which told me what I'd already grasped - that the fandom was more about the clique and their stories, rather than about the writing itself.
Hence, I write mainly for my own pleasure, and to share with mates, and AO3 is a great place because I'm very anonymous and the fandoms I write for are fairly small and clique free.