Erron black , Cassie , Ferra , jacky are not ninjas or monsters and look like MK characters . Now , Geras is Darkseid , Centrion is Poison ivy , and Kolector is Scarecrow . If you dont see the resemblance i dont know what to say to you .
It's an opinion, not a fact though that "this guy looks like this, that guy looks like that" If Injustice didn't exist, nobody would be complaining about this. Erron Black is a cowboy, honestly at first he looked like he didn't fit in that's not to say he didn't look cool but Cowboys vs Ninjas with hell powers doesn't exactly blend in most universes but that's why I said it's MK, there's already tons of variety. And Cetrion isn't
poison ivy, she's a billion times more powerful, can control ALL the elements not just the green like Ivy is limited to and would literally stomp Ivy.
Kollector's stance looks like Scarecrow but last time I checked, SC is a human with fear gas and Kollector isn't even human with 6 arms looks like something out of LOTR and Geras is nothing like Darkseid. Don't know how you're getting these comparisons honestly. That being said, Kollector and Scarecrow are nothing alike. The only remote similarity is like I said their game design fighting stance. But that's where it ends. By your logic, Erron Black=Deadshot. Clearly that's not the case just cause both are mercenaries for hire who happen to use guns.
The closest one cosmetically for someone that doesn't read comics or play MK would be Cetrion and Ivy but again, their powers are very different. The better argument would be Deadpool being an obvious ripoff of Deathstroke since he was made as parody of DS. Also, I'd gladly take Cetrion and Kollector any day over boring Jacqui. You talk about similarities, she's literally Jax female 2.0. I won't be playing Kollector but at least he's original.
As an artist myself, I can say the problem is this. People are confusing artistic style with actual knockoff. There's a huge difference. Just because Cetrion and Ivy have similar artistic styles, doesn't mean they're the same. By this logic, all the MK ninjas are the same then clearly not the case.