I've attended courses from some of the best researchers on the planet (like Graetzel at EPFL) and you did yourself a favor if you skipped the confused ramblings and just studied on the books.

Plenty of courses taught by brilliant individuals that were just bad at teaching or borderline not prepared.

Some courses (like biochemistry) were effectively useless as de facto you had to memorize 600 pages of Lehninger's book anyway. There's nothing to understand in the Krebs cycle.

I also vividly remember exams like advanced algebra were the professor genuinely did nothing but rewrite canned content on a board and could not really shed light on anything, you were on your own.