For starters, the Forsaken player race is made up of humans of Lordaeron who died from the plague - since we as player Forsaken represent a general sample of those folks, we're all undead Lordaeron humans more or less, despite that a smaller % of maybe high elves and former PoW orcs or something were living thereabouts.
As for continued undead, it's explained in Cataclysm that the Val'kyr who are now making more undead are only able to re-animate human corpses and cannot do so with any other race.
Presto.
Also, I own GW2 and I'm not certain what you're referring to - elaborate? Moreover, GW2 isn't really a good game to reference about race comparisons because there's like one unique silhouette in that entire game, the other races all pretty much share the exact same one but have different model quirks and textures or drastic size difference. WoW has unique silhouettes for all of its races, with a little bit of similarity and it's one of the only MMOs (STILL, mind you) where each race has unique animations - play GW2, FFXIV, etc... no matter what race you are, your animations are allll the same. So give Blizzard some credit, they do what they can and most of the time they do it well.
RE the OP - I think you're either severely overestimating your own knowledge or severely underestimating Blizzard's; there's a reason for the undead looking how they do and any anatomical/skeletal inaccuracy (mophological? o_O) is likely not because they don't know how ribs are supposed to face or how many vertebrae a human spine has, so while your intent is warmhearted I think, you come off as a wee bit pompous.