Because WoW had 6 years of development time after its release. Programming a game isn't just as easy as saying "This is a good idea, add it." It involves implementation which is incredibly complex in some cases and takes time. The thing that is important is how well and timely they fix/add the things that they plan on fixing/adding. Look at this game in 6 months, see how far its come and then project to how well it will be in 6 years and compare that to 2012 WoW.