They're the ones who post racist diatribes under green alt account and anti-vaxx conspiracy theories and complain about wokeness and talk out of their ass about subjects they have no actual expertise in. The ones who think flagging is just a super downvote.
I mean, the premise that simply having a minimalist layout would filter for a better class of people has always been a bit silly. Eternal September is an inevitable result of having new people join a community. Every new person, every new comment, increases entropy. It doesn't matter how technically proficient they are, they will change the culture simply by virtue of their existence and participation at scale.