I've played multiplayer fighting games, first person shooters, racing games, platformers, beat-em-ups, and strategy games recently, and I would not say that any of them were mindless. However, they were all fun.
That said, I can also appreciate a good single-player game and definitely do not believe every game should have a multiplayer mode.
I like multiplayer, but the notion that every last game needs a multiplayer mode is ridiculous to me, and I wish devs would stop. I also dislike the trend of devs feeling like the multiplayer has to make sense within the context of the game's story, to me all it does is limit the gameplay possibilities.