I don't think that millions of players would really agree with your assessment of quality. Firstly, WoW runs on most computers due to relaxed system requirements, while most new games nowadays require at least a multi-core computer with latest graphics card. The new upcoming games will require at least PS4.0, which would force gamers to upgrade their hardware.
Moreover, WoW is a social game. It is like TF2 minus headshots, plus actual socialization. People that aren't too successful in real social life suddenly find themselves comfortable on an online game, where nobody can see your acne, dirty clothes, smell your bad mouth breath or stuff.
And lastly, WoW is full of content, there are numerous things to do for each type of gamer, not to mention that it is continuously expanding.
I would know, I've been playing WoW for years. I've quit only because I wish to do something productive in my life for a change other than leading a raidguild. Besides I've seen everything there is, WoW has gotten repetitive and it begun catering to majority. My experience has been watered down.
So while I await Star Wars: Old Republic, I am writing a novel and attempting to make something productive in Construct without running into a fatal creator's block.
Don't diss WoW, it is like a succubus. Either you resist her fully or she snares you for a long, long time. She's being very successful, y'know.
Oh, the biggest thing I disliked about WoW - its subtle transition to additional pay business models. Rename your character, change gender, change realm, TCG cards... everything for money. Upcoming faction change. For money. In addition to the constant gold seller spam.
While the player has just become a number.
Fuck that golden goose, I'm happy with my dirty old hen.