Also there's a fucking gigantic gulf between both metalCORE and METALcore as bob describes which both involve synthesis of different genres into a coherent whole, and bands like TDWP which are second or third generation and are unoriginal rehashes of those syntheses, where even if they do listen to Rorschach or Dissection or whatever, it's not the primary influence on their songwriting. It's actually metalcore bands. And of course this gets even worse when the second or third-gen bands start becoming primary influences and now you've got bands like Suicide Silence or Miss May I making even more washed-out bullshit and wouldn't know Slayer or Minor Threat if you beat them about the head with it.
As the foremost contemporary commentator on Whatever Bullshit Kids These Days Are Into, Sgt. D from Stuff You Will Hate/Metal Inquisition has a pretty handy exegesis on the whole subject (although from the perspective of the skramz/screamo axis) in a guest column for Metalsucks
right nyah