Isn't general relativity framed in differential geometry, not algebraic geometry? All of Einstein's papers on special relativity use high-school algebra and calculus.
Yes, GR uses differential geometry; however, a good (mechanical) understanding of any exterior algebra helps when working with tensors; and, I found GA much easier to understand than algebraic & differential geometry, when starting out. The idea is to familiarize yourself with learning math. The actual math of the GR paper is pretty straight forward: it's the physics which is so mind bending.