I have absolutely no objection to bands evolving and changing their style. A lot of my favourite bands, both inside and outside of metal, changed drastically over the years, or did experiments in other genres: Ulver, Skyclad, Burzum, Coil, Current 93, Death in June, Ewigkeit, Borknagar, Swans: all bands where you couldn't really imagine the last album from listening to the first.
No, what I object to, specifically, is bands just becoming shit. Metallica didn't evolve. They ran out of ideas and energy.
Also, statik, I'll begrudge you your point. If DM bands were going to talentlessly copy anyone though, I'd rather they stuck to Carcass.