I guess the difference between Klingons and Orcs could be confusing to some. Vulcans have pointy elfin ears, and Ferengi are vaguely...ever so vaguely...goblinoid.
But then there's the focus on combat between interstellar starships.
And the entirely different genre.
Having recently become involved in two different MMOs with settings that are about as unWoW as you can possibly get, I still wonder what the "But...it's not WoW!?!?" crowd expected to see when they logged in a post-Apocalyptic or high SF game setting?
Again, not even remotely suggesting that the games have WoW's obviously industry re-defining polish - but about 1 in 5 of the complaints I've heard have been the "not WoW" shtick.
(Heck, after six years of WoW and shameless clones, I consider that a bloody bullet point.)