I completely agree with your points Planetary Eulogy about music and art that is aimed purely for entertainment purposes lacks the central ideological expression that makes them art at all.....i've always believed that myself....
BUT.....it absolutely does not explain or justify your ridicule of underground metal bands who aren't clearly innovating. Yes, i'm sure Death and Dimmu Borgir DID/DO have little currency signs floating in their heads occasionally, but completely disregarding them as tripe for that is flawed and inconsistent with even your own reasoning. The fact remains that these people wouldn't be playing underground metal AT ALL if their main reason was for entertainment or money...they'd be making pop music. Further, even if your argument is that they WERE starting to write accessible music (ie, melody, simple structural repetition, whatever) it doesn't follow that that means they're deliberately abandoning ideals. Its clear to anyone that Death and Dimmu Borgir play with passion and expression.....but it also doesn't follow from the reasoning you've provided that 'apeing' or utlizing musical ideas from influences qualifies as worthless music; in what way does sharing or playing music that does this instantaneously mean the artist is doing it for entertainment purposes only??? You're not a mind-reader as i've said, and you simply don't know enough about the artists' intent to damn their music as ideologically lacking...neither can you irrefutably deduce from the music such a thing. In that case, I may as well just go ahead and say Atheist were lousy sellouts playing worthless music because they had the odd melodic-sounding riff.....OMG! Ear candy!
Your beliefs (so far explained) about the philosophy of art/music/entertainment don't qualify your previous damnings of bands like Death and Dimmu Borgir.