Calculus is pretty basic and if you wanna do useful economics you need calculus to some extent (and many marxist economists use calculus) but usually when economists use stuff more "advanced" than calculus they only do it because they think it makes them more "serious" than they really are, and it helps obscure their dumb premises.

A good analogy would be using precision lasers to make extremely fine measurements to perfectly align a square peg with a round hole.