I don't think this game has actually changed all that much. It has definitely followed the general trend of casualfication, but the game started out pretty casual. The biggest issue is the content seems to be spread a bit thinner and a lot less inspired.

Other games, such as WoW, basically abandoned a philosophy of an immersive world to explore and conquer in favor of becoming an instance-centric quasi-e-sport that lives for the now and no longer rewards long-term time investment.