Speaking just for myself, I hate it because of the dev team behind it and the awful looks they give female characters. Catwoman especially stands out with her ultra masculine face. But the bigger issue is just how poorly NetherRealm Studios animates things. https://www.youtube.com/watch?v=t06Dkdg6fEo
This video kinda goes over it in more comprehensive detail but in motion, Injustice/Mortal Kombat games look terrible. Theres no weight, no flow to fighting, everything just feels stiff and awkward, theres no joy in just playing the game. Obviously if you enjoy mortal kombat games, its fun, but theres a lot of issues wiht just how the game plays out that makes it not so fun.
Tekken is a good example as a game with a ton of customization that has a high skill ceiling that still lets you get away with mashing and just enjoying a lot of SP-focused stuff.