uhm... For me, I only really interact with character analysis accounts or fanart accounts in my fandoms. and people are relatively fine in both. so i'd say my fandom experience has been pretty alright
from what i've seen of the entire fandoms though, genshin is uhm. annoying. like the aether harem people who draw the women strangely are annoying but a lot of the main mlm shippers (haikaveh, chili, wriolette, etc) are annoying too... but it can also be really creative, I've seen a lot of cool work on the subreddit.
For project sekai, from what I've seen from Instagram comments they're annoying too. okay but weird thing is I feel like PJSK fanartists always have such a cute art style it's insane
for BSD, no media literacy as people have said, but again I only interact with fanartists and analysts so my experience has been pretty pleasant...
for csov, I've actually never really got into the fandom so. but people who look at Vanitas under a telescope are so cool like kyahh stop picking my brain apart... I love u... u get it...
vocaloid is chill we just vibe and idolize miku
uhmm. uhm. what else. yeah I think those are my main ones