First of all, screw you, you speciest hominidophile. Second, a bipedal form capable of clasping motions with the hands and feet would be one of the most useful forms that can be taken, evolutionarily speaking, and therefore it's easily acceptable that both cats and raptors could have gotten there. Furthermore, the humans and elves came to Tamriel after both the Argonians and Khajit were there, which makes them the weird ones. Yet more, there are plenty of differences; you need only look at the cultures of the various peoples to see how they have grown and adapted to their environments. Take the Hist, for example, or the Argonian predisposition to being less susceptible to disease, having survived the impossibly harsh Black Marsh.
But, that's not your argument (mostly). You are annoyed by a few things that basically come down to this: Short of creating entirely different physics for each race in what is already an enormous mountain of a game, and short of literally retconning their past few games in terms of race dynamics, making their movements and animations the same was the only choice. In doing so, they don't have to remap the collision lines for the armors, they don't have to recheck the interactivity between the map itself and the character models, they don't have to have redesign the movements of two races as they interact with items and people in the environment, and they can continue making the game as large as it was.
But, your other issue comes to this: We are humans. Our Gods have been human, or, at their most different, humans with animal heads. We're extremely bad at coming up with believable creatures that don't act like us, look reasonably like us, and resemble us, because if they stop being close to us, then we cease to believe they're anything as grand as us, or have anything to do with us, short of feeding us, or eating us.
I will, however, give you that Argonian females should not have breasts. That's just terrible design. Which, again, comes back to that whole "human" thing, and how because our females have breasts, we expect all females to have breasts.
Besides, it's fucking awesome not to have my choices limited to "variant of human/elf/dwarf" in a classic fantasy game. If they threw in an avian race alongside the other two, I'd pop my lid.