I think a lot of us (ok, maybe just me) have gotten quite used to some of the quality of life changes that have come into the game over recent expansions. The thing I am curious about is how 'pure' vanilla will be.
For example didn't IWT only come in with WotLK? If I remember that correctly then running a melee team or questing is going to be REALLY fiddly if it turns out to be a pure vanilla build.
Other than that the new expansion looks interesting, definitely looking forward to it - the void elves look really cool. I'm a sucker for levelling so the scalable levelling experience looks fun. Also think the island expeditions in PVP mode could be really cool (if follow is allowed ofc)