They spent a lot of time and effort on predatory systems, very likely, because their bosses demanded they meet specific retention/play time goals. From my understanding, there's a lot of evidence that the more time players spend on a game, the more likely they're going to spend more money on it.
Really, obstensibly all the major problems with Blizzard stem from corrupt/bad upper management, not the devs.
The company is too corrupt and morally bankrupt to get to this game to a point where it will ever take off again. And "more content" from these clowns just means more mount colors and a handful of mindless new quests with little to no substance.
There's a shot Microsoft could fix a lot of the issues, but that is a while off and probably not likely.
My guess is WoW is dead as far the mainstream goes. Like actually dead. Other than the month a new expansion comes out, people with emotional and addiction issues will almost entirely be the only ones playing WoW going forward. In fact, that already seems to have happened.