That maybe true but at lease we can under stand the lyrics unlike a lot thrash metal they pick
Zynthetic, Rocky Gray it ok but still not cup of tea as I don't like metalcore sound type nor with hard vocals nor fast talking B.S. that in Impending Doom, Demon Hunter, Living Sacrifice.
If you listen to "proper" death metal, you're a fool if you're hoping to understand the lyrics (a lot of deathcore/metalcore bands try and fail to get the death metal sound, so it just sounds ragged and angry as opposed to brutish and evil). Listen to something like Cannibal Corpse, Devourment, or Dying Fetus, as opposed to the previously mentioned metalcore/deathcore, you will have even less chance of understanding the vocals.
You're judging metal subgenres based on how they match up to stuff like rock and hard rock. But they don't — by design, they don't. A lot of rock music holds the vocals up high, and it's important that they're understood, hence why they're sung. But it's kind of the opposite with extreme metal, they're treated as a form of flavouring. With death metal as an example, low gutturals create some kind of ambience, as if they're just another instrument.
And cleaner-sounding hard rock bands just don't really fit KF. I could be really super into Lounge music and enjoy listening to it whilst playing but there's no "feelings" involved in that music that match neither KF's gameplay or aesthetic. Not all metal genres will work either - Doom metal is generally far too slow-paced, and Power Metal is too uplifting and fantastical for KF2's grotesque images.
KF2 is an action-packed gore-fest body-horror rollercoaster ride with a sprinkling of science fiction.
Industrial metal is one possible great fit. You got heavy detuned guitars, heavy drumming/bass, and a sprinkling of electronic elements. That invokes images of action, badassery, explosions, darkness, and technology. Thanks, zYnthetic.
I still woulda liked to have seen some sludgey gut-wrenching mindless goregrind, but I think that woulda gained the game negative reviews from the mainstream.