You seem to be confused. Yes-men were often rather smart. They said yes in a ploy to get what they wanted, like a promotion and higher pay.

Lemmings, sheep and such weren’t necessarily not thinking, they are drawn to being part of a social group and follow it for a sense of belonging. They often spend a lot of time thinking about how to stay part of the group.

Doormats are people who avoid confrontation, and again, they think about it a lot, but find themselves unable to stand up to it.

There are of course people who just have low IQ. But I assume you aren’t belittling them for using AI to help them do what they can’t.