IMO the visuals were just... bland. Everyone wears grey and lives in dark grey dwellings. The color balance is so bad that Atreides flag that is green on Caladan becomes cyan on Dune. This greyness also ruined the supposedly-awesome scene with the worm where it was just a dark blob on a grey background. And it was unintentionally funny when the camera pans over a featureless grey desert, and someone says "you can tell the spice by the color of the sand".
Perhaps there was something wrong with whatever setup you watched the first one on. The colors were all pretty warm and...sand-colored, definitely not anything I'd call "grey".
