I don't think there's a "unified 'they'" in the sense of, say, there being a Stamp Out Critical Thinking Council with meetings Tuesdays and Thursdays. But I do think that people who rise through power systems while seeking control are going to be averse to critical thinking in their underlings and their social lessers. I think that's in part because most systems like that select for that kind of person, but also because it's in both their personal interest and that of the system they've hitched themselves to.

So the "they" here isn't a unified, coordinated group. But you'll rarely find those in structural problems. But there is a "they" in the sense that we can define a set of people who will act to oppose critical thinking either through direct self interest or class interest.