I don't look down on Earth ponies for not having those added abilities. They are a successful species on their own who could easily survive without the other two groups.
They fill their nix and do it superbly, what is wrong with that? SO they can't fly, why would they need to? cast spell? They can survive without that!
Implying that there is a disadvantage is discriminating, same thing that happened with derpy.
AJ is one of my fav ponies, so I don't take kindly to that.
~Lyra