that's because the late 80s/early 90s death metal scenes of new york, florida, england etc were nearly a culture and way of life...every single one of those bands (carcass, cynic, malevolent creation, demilich, resurrection, Atrocity, Brutal Truth, morbid angel, deicide, obituary..the list goes on) were different from each other musically. Yeah the majority share the same standard death growls one way or another, but death metal vocals came about at the same time and didn't last 3-6 years or so with just one band. Death metal was a scene of music and still is today more or less.
Children of Bodom were a completely different band, not involved in any scene whatsoever with a sound of their own...they had some stratovarius, a nasty punkish black metal edge, with some virtuoso guitar/keyboard interplay with melodic folkish style melodies. It's pretty insane for band like Norther to come out with bodomish-album nearly 5 years after "something wild" was released. same for Skyfire in 2001, Immortal souls in 2001, Imperanon in 2004, Kalmah in 2001.
Some of the other bands in European countries who use Gothenburg styles or any other styles from a scene contain other musical elements to them that are original...except for Hatesphere, but you know what I mean? Zyklon don't sound like COMPLETE rip offs like the bodom clone bands... They have a huge Morbid Angel influence but Daemon from Limbonic Art brought his own original atmosphere on "world of worms" and it still continued in the next release...so for you to call that band generic is just totally ignorant. Bloodbath clearly stated that they're paying tribute to old school death metal, so if they can admit that...bands like Immortal souls and Norther should too. as for Hate Eternal? Erik rutan was part of Ripping Corpse in the late 80s/early 90s with that killer album "dreaming with the dead", as well as Morbid Angel from 1994-2002...so he can do anything he wants.
Death metal was a scene of music as whether it was Canadian dm, or Stockholm dm...Children of Bodom were a band who stood 4-5 years with their own sound.