Applying derivations that someone else invented doesn’t require “pure genius”; it only requires you to be able to follow the person who discovered it, which is a lot easier than finding it yourself.

> The only way I got through my undergrad math was by doing problem set after problem set

It sounds like you didn’t really understand what you were doing then. It’s hard to phrase this without just sounding like I’m bragging, but I never had to practice doing anything I actually understood. If I felt like I needed practice, that was a sure sign I didn’t get it, which I always tried to fix with careful thinking instead of repetitive memorization