Then how do you improve? Currently there is no all encompassing theory for the design of languages or anything. So there's no prove-able way to design a langua

Then how do you improve? Currently there is no all encompassing theory for the design of languages or anything. So there's no prove-able way to design a language that can always be improved and always be backward compatible. I imagine that such a language would be incredibly simple. Minimal syntax and all sugar and conveniences would be built with libraries.