I've played AO, AC2, DAoC, COH, Matrix Online, PS, SWG, SB, DC Online, DAoC, SWTOR and here's what I've seen. Since WOW dropped, all I've seen are devs trying to duplicate WOW's themepark design thinking they can also get 10 million subs. No major studio has tried to make a sandbox for the past 8 years. Features that used to be MMO staples like player housing, nobody's putting in games anymore because WOW didn't have them. WOW's main innovation, leveling through questing, is now in every game.
If people aren't getting sick of the WOW formula, I don't know why every game that's used it (which is pretty much every recent MMO) has either lost subs or has had to go f2p to survive. It's been 8 years already, the last expansion was underwhelming, the highlight of the newest one is you get to be a panda. But WOW still holds marketshare. Because devs like Cryptic, Bioware, and Zenimax think they're innovating when they're just reskinning WOW