Having imagination doesn't matter if you don't understand what geniuses came before you and what they interpreted and misinterpreted about the world. His theory upended Newtonian physics on some level, which is the practical basis for Calculus in the first place. You have to understand those concepts on a deep and abstract level to be able to challenge a dominant, centuries long, paradigm like that. Imagination without complex, higher order, mental models is useless for discoveries like Einstein's.

It’s not that his math skills needed brushing up. Noether’s Theorem was proven as a result of the need to for conservation laws in his theory of general relativity. She discovered (invented?) the mathematics that demonstrated the existence of conservation laws. Needing mathematics that hadn’t been discovered yet does not count as an example of his math skills needing to be touched up here or there.

I'm talking about her contribution towards general theory of relativity itself, not her other creation of Noether's theorem