I have never believed in the phrase, "that's not music," even when it comes to music genre I don't like. I may not like it, but I'm not going to try and claim that it's not music.
That is... until I heard Cradle of Filth, Children of Bodom, and the like.
Why? Because, in my opinion, the ear-bleeding levels of screaming/growling overpower the instruments. You know the things that are suppose to give the song rhythm. No rhythm, no music.
It's kind of like those female singers who are so revered by music critics because they can hit the really, really high note. Ever listen to one? Tell me, how many here actually go "Ack!" and whence when they hit that high note? I do because to me it adds nothing to the song. In fact, I find it distracting. Death metal, (I'll just call it that here for the sake of time), has the same problem except it's actually worse.
I've lost count of the number of times I heard a metal song start and it sounds good. Then the lead singer has to open his friggin' mouth. Nothing ruins a good song like hearing, "mooorb dooupoooomaab togrooooooollllllll!!!" That is seriously what it sounds like to me.
That's the problem with most death metal and screamo bands that I've heard. All of that screaming and growling actually serves as a distraction to the music. Lyrics should never distract the audience from the music.
I grew up listening to Iron Maiden, Metallica, Megadeth, Ozzy Osbourne, Guns & Roses, and Motley Crue. So maybe I'm old fashioned.
Now having growled/screamed lyrics doesn't always automatically make the song suck. However, there are only two songs I can think of, off the top of my head, where the growling/screaming doesn't distract from the music.
Note how the growled lyrics are never louder then the bass guitar. Helps it go along with the song instead of overpowering it.
There's screamed lyrics, but it's infrequent and done by a back-up singer. Thus it adds to music instead of being a distraction.
Yes, I acknowledge all I said above was subjective opinion, and NOT objective fact.