People really tie "kills" in games to murder in real life way too casually. When I play a game it's about strategy, team work, and winning.
A lot like Football (Soccer). It has little to do with the terms or animations used in the game -- those are just for entertainment.
I don't play a game because of how violent it is, I play it if my friends have it and/or it has good/fun game mechanics.
The special effects in a FPS might provide maybe 1% of the total entertainment of a game.
Another interesting analogy is PG or TV-scene edited violent movies. Despite "Fight Club" G rated TV mix only being about 45 minutes long its still interesting and entertaining without the GorePorn.
Speaking of pr0n, romance/drama movies aimed at women are essentially two hours of pr0n foreplay with the X-rated visuals removed, yet are generally pretty good sellers to the mass market.
To some extent the only reason we have ridiculous over the top gore in FPS (and horror movies) is we have recently gained the computer tech to do it, so we must do it to extremes, and there's people trying to stuff their resumes with ever higher numbers of buckets of blood. Once that market weirdness is past, the GorePorn will decline a bit in popularity.
As an example Fortnite is new and somewhat popular yet about as gory and bloodthirsty as playing laser tag. Its not exactly Killing Floor or even Half Life which peaked at perhaps 100x less popular.
Why would it? Furthermore, does this mean we also believe that people who do stuff like karate or Judo are more desensitized to violence?