For me, WOTLK was the last great xpac. We got some great features in xpacs following it (things like account wide mounts, transmog, pet battles), but the xpacs after wotlk have all made great leaps away from the "feel" I got from Vanilla-BC-WOTLK. As much as people extol the virtues of MoP, I think it did tremendous damage to the game. Things like making dungeons irrelevant, gating everything behind rep that was gated behind dailies, requiring rep to actually spend the valor you earned, and my personal pet peeve that still exists today... rune of power. Some of that was eventually fixed but ultimately from MoP and beyond is when I lost confidence that Blizzard could provide me with a product I could fully enjoy. WoD was even more damaging to the game. I will say though that legion made great strides in repairing that damage.
Every xpac since Cata though, has been change for the sake of change. As far as I can tell Blizzard hasn't made much effort to "keep old nostalgia". From my perspective its been a constant routine of: new xpac, invalidate all efforts that came before, change for the sake of change, because round wheels are old and we need a new shape of wheel regardless of how well round wheels work, treadmill till new xpac, rinse and repeat. About the only consistency I can expect from WoW now is that few things will remain consistent from xpac to xpac.