You don't discard Newton. Newton becomes the limiting case of how you would apply Einstein's theories.
Newton, Einstein, and every other great scientist in history...They all made mistakes. Of course they did. They're human! Science is a way to keep from fooling ourselves and each other.
If you look at Einstein's equations and put in low speeds and low gravity, they become Newton's equations.
Newton came up with Newton's laws of motion and gravity. They worked. They were working.
