It's mostly due to older players getting bored. Sure there are some areas which damaged like the raid thing. Raid vanished. Think only Japan clears it now and even Yoshi stated that the Japanese do not care about the gear and rewards and like to clear the content just for the fun of clearing it. West doesn't work like this and Yoshi failed in this regard. The game is still healthy and kicking. Also if you expect that the game will evolve into the old school open world sandbox games then you are playing the wrong game. This game is supposed to cater a more casual audience who like to play this game few hours per week. It's supposed to rival WoW and not for example EVE or XI or any of the Korean hardcore grind on the open map and get KO'ed by another player MMORPGs. That being said this game has still a lot of things waiting to be done or improved. In few days when 4.0 will be revealed and excitement will be back.