If you want to see a promising MMO crash and burn, follow ESO. The developers there have their heads so far up their behinds that the game is in some serious trouble. It might even break the record of "fastest to F2P".
I just played it for the first free month and it was brutal. Constant 4-6h maintenances, unplayable lag in PvP that only started recently (was fine around launch). People freely exploiting infinite resource spawns for weeks with nothing being done. Skill lines where literally not a single passive works. Completely out of whack difficulty where monsters just get an increased hp pool and damage done across the entire zone with no testing done, resulting in certain mobs taking minutes to kill while others only seconds. Completely unkillable quest bosses because they just oneshot you with abilities that you have no way of avoiding due to lag spikes.
I could go on for a page, but that game is a mess.
This is why companies need long alpha and beta tests. Real testing not another way to pre-sell the game.