I don’t have an aeronautical background at all, but a hunch I heard from some aviation forum is that the plane must be certified to be safe when flown by merely

I don’t have an aeronautical background at all, but a hunch I heard from some aviation forum is that the plane must be certified to be safe when flown by merely an “average” pilot, and if the Max was more difficult because it had this tendency to stall, that might mean it needs a pilot with more skill, therefore more training for existing 737 pilots. So MCAS was needed to ensure no skill difference or training difference whatsoever for the pilots, even if a typical pilot should be capable of flying without MCAS.