My real issue with the "cartoon" look isn't with the brightness and saturation, I just thought those were elements that could be easily adjusted, either by the devs or the users.
My real concern is the graphics themselves look child-like, as in a game designed for young children. It just comes as a surprise after hearing the descriptions of the game from devs like "A bloody, deadly war with orcs."
I don't want grim and gritty, just something with a tone like original DD or DD2. DD was all 2D art of course, so it's going to look different no matter what, but still, the graphics looked crisp and detailed. There was also an element of realism in enemies and weapons. Same with DD2. Right now it looks like I'm fighting monsters from Pixar films and Super Mario games.
Evolution of Trolls in DD-->DD2-->D:OS?