5e is less a well-designed system than a well-edited and playtested system. They basically kept lots of interesting ideas and simplified things where they could apply unifying ideas (like advantage/disadvantage) but left well enough alone when they couldn’t.
5e is like a good Shakespeare modernization that cleans up some of the archaic language where it was getting in the way of comprehension but knows to keep “wherefore art thou Romeo” because everyone expects that line in Romeo and Juliet, even though nobody says wherefore instead of why anymore.