Your DM is simply not a good DM and they would probably be a bad player as well, because of the simple reason that they didn't understand the basic premise of DnD.
DnD is a COLLABORATIVE storytelling game first and foremost, and only then is it a roleplaying game, a fantasy combat game or whatever you want it to be. The entire game is about working together to create a story. If one of the players (including the DM) doesn't understand that, they will invariably fall into one of the multitude of 'that guy' tropes.