I dont think anyone ruined WoW. I just think a game that has been out this long and with its low graphics, has done a pretty amazing job at surviving this long as an MMO that still does subs of more than 1million.
No one likes change. Thats all there is to it.
Casuals and Hardcore can moan and complain all they like because if they didnt moan, I would be seriously worried.
The only thing that is going to ruin WoW is time and how they deal with more and more content being added ( removing content will just really piss people off but something has to be done to the stuff that hardly gets used)