What's a fanfic pet peeve of yours? either when writing or reading

I see this is often in new fandoms, when the media gets revived interest or in older works in the fandom. It's when pairings or a particular character get's infantilized or feminized.

Now I don't have an issue with feminine characters or people with feminine traits(whether they're a man, woman, both, neither, or other) it's just when that translates to fandom they get written without autonomy over their lives and are mostly present in exaggerated stutters, cute clothes, and to be in a relationship. The character doesn't even need to be feminine, just being short or somewhat nice damns them to be the O in A/B/O for eternity.

I've had the unfortunate experience of actually reading this in a lot of mlm ships when I was in middle school (2018 was fucking brutal ifykyk) it was like a crash I couldn't look away from. Occasionally there's still works that rot my brain cells away by the minute but I don't think of it so seriously.