Basically this. If they had slowed down releases, even added new songs as updates or micro DLC packs in between, I think they’d have had something that would’ve worked for years. It was incredibly popular because the variety of play was big and the controls for each position were pretty basic enough to the point that anyone could pick up any position and play.
However, everyone had to have their own version inside of a year. DJ hero, American Idol games, every major band of the last 50 years got their own branded version of Rock Band, etc. It burnt the market out like the Great Awakening.