I agree, actually the courses I never did well in was because they just weren’t challenging or from not learning anything…I always succeeded in the hard classes.
If a class was easy I personally felt it was just a waste of time and bogus (for me) and never felt why I should put so much effort into something I know.
For example: If I make you take an addition class — and make you do 300 adding problems. Will you do it? Probably not, it’s a waste of time to you and you learn nothing from it.