I'm a humanities student and not on the left. My experience with leftist professors is that even if they try to actively push their politics on students, they will still give As to papers with well-reasoned dissenting views on highly political topics, immigration for instance. The only unfairness is that students who just repeat everything the professor says in their paper will get an easy grade without much thinking but I don't know what can be done about that, unless professors are to penalize unoriginality. The groupthink isn't an obstacle to critical thinking, it's just an excuse to avoid it.

Critical thinking skills aren't something to have on top of domain-specific skills, they're something to have as a foundation for them. If you focus on critical thinking skills in lieu of anything domain specific, and expect to get a job without further learning, you're foolish, but you'll have an easier time learning the specific skills you need for practical work anyway.