Luckily I've usually noped out of the groups before I think there was too much lasting damage for me, minus the general weight of how the same damn things keep happening, and how so many places that should have "felt like home" aren't places I want to be.
Perpetually feeling like the outsider among supposed outsiders isn't great! Though at least looking back now, I also have more of the "man, wtf was that shit" feeling, rather than the confused/hurt feelings I used to have.

And yeah, it is a terrible mix! Boundaries for me, but not for thee. *I* must be catered to, but trampling YOUR boundaries is just funny!
Ugh, ew ew ew at the "fandom mom" thing. I hate that general term, and I really hate that you were pushed into it (or that they attempted to do so.) Gross. Like... I am not your damn mother, and I do not want to be.

We have talked about that, and it absolutely tracks with basically every group I've tried and failed to become a part of. The people you would actually like to meet and hang out with nope out because of the bad behavior, leaving an increasingly self-selecting set of people who are DOING the bad behavior, or who are just willing to tolerate it because they feel like they should or have to. So bad boundaries from one side or the other. Like, a lot of these groups are supposed to be full of weirdos, and I have a decently high tolerance for weird! But not boundary crossing, hypocritical, rude, bad behavior.