For instance, we all probably had to go through math classes where the professor writes so fast that it's a hand cramping race just to even scribble together enough notes to follow each gigantic derivation later for learning purposes. Nobody in that class is retaining any of that.
The kid who aces that class, is almost invariably someone who likes to to play with the equations in their free time at their own pace, so they get a feel for what process they need to employ toward a solution rather than brute forcing it. (When applicable, sometimes brute force is the only tactic.)
Math classes in general really, desperately need to slow down and let students grasp higher-order concepts. The number crunching method is stressful, and all it does is massively discourage bright people who may be geniuses in their field but flee University because the school made Calculus their "breakout" class.
Anecdote. When I went to University, I had a professor who graduated MIT tell the class that he'd realized how much pressure we were under in our Calculus class trying to keep up, that this was deeply unfair, and that he was erasing our last test score because they were unreflective of the performance that he knew we were capable of if we had any time for his class. Calculus was a core requirement, his class was elective, so almost every student had been forced to ignore his class, and we were amazingly lucky that he was good enough to sympathize.
This man used to work at Bell Labs and swam 200 laps a day to keep fit. And he was telling us we had it rough. I saw people cry out of gratitude.