That makes no sense. We only have 2 Kryptonians on the rosters and WAY more humans. Explain to me how having one more Kryptonian is a problem but adding another human is not? Hell, I'll bring up the fact that there is no female Kryptonian in the game, yet numerous female humans. Actually, there are already three form the batman universe alone...and people want to add more...yet claim its for diversity or they "deserve" the spot more? What?
I meant Kryptonians in the sense that they all have those powers. And that is obvious, so it does make sense... None of them are particular martial experts or anything. They have one, specific and defined set of superpowers, and that is what they use to fight. All the humans in the game have different things about them that lend themselves to a fighting game character in a unique way. Green Arrows bow and arrows, Bats tech and martial arts, Nightwings sticks/staff, etc. The Kryptonians don't have those unique differences amongst how they fight. At least none shown in the comics, movies, shows, etc. There is functionally no difference between how Superman fights and how Power Girl/Supergirl fights. Period. They managed to stretch things with Zod, and it worked alright. Doing yet another would just be too much, I think. And I can't fathom how others wouldn't see it that way either.
And for the record, I'm not into having anymore Bat characters either really. I'd make an exception for Poison Ivy, because again, those are completely new and unique powers not presented in this game.