It's literally Mists tier of new stuff- new race, new class, talent revamp, some other core system changes (professions for DF, cross-realm for Mists) and one signature feature (Dragonriding vs scenarios). And Mists is often cited as one of the game's standout expansions because what it did, it did splendidly.
Personally I'm all for an expansion that does what it wants to do and does it well rather than Blizzard's fifty shades of reinventing the wheel. It mostly worked in Legion but BfA and SL were other stories.