And yet Legion was the expansion that kept the amount of players playing most steadily since WotLK. First expansion in 6 years that managed that. Read MAUs from back then. Remember this is the game director and team that gave us Legion, not only WoD and BfA which indeed got troubles, but that got little to do with "diablo mmo".
And the game is just as much mmorpg as it had been since WotLK. Contrary to belief, the game philosophy we have now is the same they started with in WotLK, for many the best time in World of Warcraft. We need to go back to TBC if we want anyhthing like the MMORPG parts you are looking for.