The way I see it, a lot of this stuff isn't even mainstream. From what I understand, a good amount of anime doesn't even air at peak times or on popular channels in the first place and on top of that how many isekai anime (although I don't think the problem is isekai, I think it's light novel adaptations) can you count that have had any lasting impact on either Western or Japanese anime/manga culture?
What, like Konosuba, Overlord, Goblin Slayer I guess (but that feels like more of a Western thing given never getting a second season), Re:Zero, Mushoku Tensei, Sword Art Online, this is digging really deep into an entirely different era of non-isekai slop but Spice and Wolf; I'm counting specifically things where characters from these series have had a lasting effect on the culture, evergreen waifus/husbandos, etc. and you can really only count them on two hands, maybe a bit more if you stretch. I just realized you kind of had the same point as me; yeah no matter where you go people make awful content; I think weebs would see a lot of parallels between themselves and the conflict between the booktok community and the "contemporary" book community if they checked.