I had this same experience. The professor would say just read the book. We would say but we did read it and we are confused. And he would say I don’t understand the issue it’s very clearly stated in the material.

In fairness I actually did have one good experience with this. I had a history professor assign some material he’d written about the civil war and both he and the material were fantastic. Ironically that was at the junior college. Professors become professors by publishing. I’m not sure why someone would think “wrote the course material” would be a feature unique to elite universities.