Human barely has negative, and it's positive interactions aren't positive enough. There are cards in Genesis that need a human pilot to be able to function. Problem is, those cards rarely see play because of that restriction (and it's too costly for what it does). On the other hand, only two cards have an advantage against humans, and one of them rarely sees play while the other is human himself. Unless there's some cards I'm missing, Human Subtype doesn't really have that big of a disadvantage.
I agree that it would be nice to see support cards for other less used subtyping, particularly the magic subtype on certain abilities which seemed to be put there in preparation for something, but as of yet remains unused.