New levels
New zones
New quests
New dungeons
New raids
These are the things that I'm looking most forward to each expansion. I think that since Cataclysm or so there has been too much focus*** on "new features" (Pet Battles, Garrisons, LFR, ...) and changes instead of what I'd call "raw content" (listed above). I'd argue that most players don't want the game to try and reinvent itself each expansion or even in a patch. This is what has happened several times though, just compare the way levelling, dungeons and raids have been experienced in each expansion. Take a look at the 100th change to raid difficulties in WoD (this thread is not about raid difficulties, just a concrete example of the kind of changes I'm talking about).
TL;DR: New features and changes each expansion detract from the original core features of WoW, listed above. I think expansions should put more focus on simply adding more content. Am I alone with this mindset, or are there more people who just want to enjoy WoW the way it is?
***I think I should clarify that I think the community has put too much focus on such things ("Why are garrisons the only new feature in WoD?") since Cataclysm or so. Blizzard has obviously been changing up WoW since the beginning. For example, TBC brought forth massive changes to the listed core aspects by implementing flying, heroic dungeons, dailies, raid size changes, etc.