With MK specifically I'd like to add that the PTSD those developers / artists etc. got was for an aspect of the game -- fatalities -- that in my experience most people stop even using after they've seen all the animations.
Maybe it's different with the newest one, but I remember after the first two or three months or so people just stopped doing the fatalities because it's just a cutscene to sit through before you get to play more game, since you only do it after the fight is essentially over anyway.
To the broader point about the acceptability / existence of ultra-violent / gory media in a hypothetical left-wing society: sure? The traumatization of workers is unacceptable, but the work they did now exists, and can be copied by future artists without having to directly subject themselves to snuff films and garbage like that.
There might be some impulse to pursue even more realistic depictions of the gore and death, but I hope a socialist / communist society could remember the value of artistic license over blindly pursuing ultra-realism. Besides, IMO the thing that made fatalities entertaining in the first place was more about how over-the-top they were, rather than being revolting or horrifying.