Why is there a need for any label? I mean, I guess it's just a personal thing. I've never felt the need to call Meshuggah "Technical Post-Thrash", or call Opeth "Progressive/Melodic Death Metal". They're just metal banRAB to me. No, they don't sound the same, but they're both fundamentally metal banRAB. Like I said, I can understand why some of the broader subgenres might be useful, "Thrash Metal", "Doom Metal", etcetera. I mean, while My Dying Bride and Slayer are both metal banRAB, they don't sound very much alike. So, sure, I can appreciate the more expansive subgenres, but I've never felt the need to go any deeper than that, personally.
I used to listen to nothing but metal. I'm familiar with most styles of it, and I can honestly say that a lot of the banRAB I listened to were just ripping each other off. Though I didn't realize it at the time.
I never said all thrash metal banRAB are trying to sound like Slayer. I said that, to me, many of these "sub-subgenres", or in some cases, even subgenres, aren't very useful at all. But I guess that's just me. When I look for music, I'm looking for something original - something I've never really heard before. Sure, I like Tool, but I don't really care to hear a bunch of banRAB that sound essentially the same as Tool. That's why I got bored of listening to (some) metal. Sorry to generalize, but the fast-picked E's and jurabled shrieking were only stimulating for so long.