Jeeez!! What the hell happened to death metal in the last ten years or so? ... Whatever happened to the days when a death metal band would rock your socks with heavy MUSIC and not a bunch of damn gibberish?
Pretty much because Rock and Roll (of which death metal is but a sub, sub-genre) hit it's sell-by date about ten years or so ago. Kids with talent have been going in a different direction. We've had several bands lately that bill themselves specifically as Post-Rock. Rock is not dead, any more than jazz or any other music ever dies. But it reaches a peak, past which it becomes all but impossible to do much of anything new with it anymore. Just like in the sixties talented kids moved from doing jazz to rock, they've now moved from doing rock to doing other things. Almost anything else.
The 'cool kids' (and ever generation has them) are not interested in that stuff anymore. It's pretty much just a middle-age deal now.
They just had the BIG 4 metal show in Coachella, and you get Metallica, Slayer, Megadeth and Anthrax on the same bill. Hell. Most of the guys in those bands are late 30s and 40+ years old now. Their fans are not much younger anymore either.
I think in part -and I've talked to a lot of different professional musicians about this and they tend to agree - that the internet has had a huge impact, and not just in distributing music (which is has, just try to find a record/CD store anymore) but in this way: Pretty much all the music that has EVER been recorded is now available for anyone with a net connection. All of it. And given ALL the music that has EVER been recorded, what exactly can you offer up that is new, or different, or even exciting? It's going to take a good ten or more years to really digest all of that, and what is going to come out is going to be a super hybrid that takes into account all of that other stuff and finds a new way to combine, synthesize and create it.
But, for the "Rock is Dead" fanclub, I'll offer up Rock of Ages as it's headstone. If Broadway is making musicals using power ballads as it's core score, you can bet the kids have long since moved on elsewhere, and all that's left for fans is middle age folks.