aside from any personal preferences, such as it looking very cheap, and quite often resulting in visually incoerent games, it really prevents people from improving as artists, it creates this weird myth that art is this inaccessible skill, which is really untrue, some basic understanding of shape theory, and what colours work together and you could really make something truly unique and special.
It's a shortcut that if more people were to take, we would have a lot less visually distinctive and fun games.
ai is a tool alright, just one that in my opinion hinders future growth as a game dev/ artist and in the long run severely limits yourself