No, it is not about flying or any of the usual complaints people have. I think WoD has really damage the game in its foundation.
In WoW you always were A hero not THE hero. Yes, you were strong, I did fantastic things, but you were never on a level with the big lore heroes. Over the time you were getting some recognition, like in Ogri’la or from the Skyguard, who knew your name and were thankful for your help. But for example in Pandaria you were still sleeping in an inn and even with the legendary cloak, you did not change history all by yourself. You were always part of a group and some of your finest moments, like the defeat of the Lich King will never get you any recognition.
But now with WoD players get the whole Mary Sue treatment. First time in Ashran, the NPCs tell you, how happy they are, that you are here and now things will change for sure. You are the commander of a whole huge fortress and in command of a small army. Now in 6.2 are a getting your own fleet, with a carrier and battleships. So you are about as high or higher in the command chain as Tailor or Nazgrim.
How the hell do they want to continue now? So what happens after WoD. All your men just leave you, because of reasons. All that military force you commanded is just gone, because it has to. It’s not like you screwed up. No, you were very successful. This is such a moronic expansion. Yes, we wanted housing, but a house is not the same thing as a garrison. Now players are the hero of a game without a real player hero and they get used to the hero treatment. Everything less than that will be regarded as a huge downgrade.
Blizzard screwed this up big time, all that time travel nonsense is nothing compared to this. And in my opinion will haunt them for a very long time. Now players want to be the special snowflake they are in this expansion. Who want's to go back to a small inn, after you had your own castle.