I think that the main reason this game is as good as it is (which is not good) is that they didn't bother to make a new engine from scratch and tried to build on top of the dos engine instead. And it just works poorly for a dnd5 game.
Second reason is that they're inprinting too much of themeselves into the game instead of neutrally realizing the fine system and world that already exist. DnD and Forgotten Realms in particular have character (strong and recognizable), you don't have to bring yours to make it alive/interesting, it's already there. You just mess the things up.
