They didnt try to do much of anything different other than fights. Genocide ending is a non-ending because it doesnt make sense with what comes after in Undertale. The worst part was definitely the frustrating fights (yes, those two, especially the latter), and the endings. The endings, for both pacifist and genocide suuuuuuucks. I think anyone could think of those as being the ending to the game but then quickly go "nahhh... that would be dumb and stupid and terrible...". All that said, game is actually fun and good for most of it. I just wish a lot of it wasnt boss spam fights and that there was more story.