I don't think people "hate old Metallica material"... They're just saying they rather not hear a band like Trivium use the same "sound" as "Metallica's old material." I agree to an extent. I'm not going to judge the album before it's released, but I have to say that it sounds like Trivium's lost some of their creative edge and traded in a distinct sound for the one they've been compared to (Metallica). I'm starting to believe Trivium took the comments critics praised about them being "the next Metallica" a little too literal. I think the reason they were presented with such a prestigious comparison was because they had something that made them different from the other rock acts out there... Not because their music/appearance resembled that of past Metallica.
It's Kerrangs fault, they approached Trivium to do a Master Of Puppets cover for that Metallica Tribute CD and everyone in the band loved Matt's new vocals so they went with it. Fucking Kerrang.