i think there's a definite tendency for people to confuse "moving forward" with "doing their own bizarre thing off to the side". take a guy like captain beefheart for example. back in the day he made some of the weirdest and most ingenious music ever, but did he really move things forward? no, because not enough people knew about him and no one could imitate his music. i think naming very obscure bands that make strange or extremely unique music is a bit of a mistake here because they're statistical outliers, and have little effect on the music industry.
i'd say MGMT is a band that really pushed music forward, not because they were incredibly adventurous but because they were/are rather different, popular, and inspired a bunch of other artists to follow in that vein. Cee Lo Green is another one, both with Gnarls Barkley and his solo stuff. he's pushing music forward with a totally modernized fusion of all sorts of black american pop music, and has definitely raised the bar for vocal virtuosity among rap artists.