Ranking of each genre's overall metalness in order from most to least:
Trad metal
Power metal
Thrash metal = death metal
Doom metal
Groove metal
Non-prefixed black metal
Prog metal
Metalcore
Alternative metal = nu metal
Goth metal = folk metal
Prefixed black metal
I'd say a lot of extreme metal has surpassed trad metal in terms of metalness. It's like evolution.
I'd agree with doom metal over thrash and death if there weren't so many polluting stoner and prefixed xxtreem doom bands these days.
Which metal are you speaking on behalf of? Because anybody even slightly into metal would surely have noticed the massive shift in direction lately with metal musicians. In many ways, backwards has become the new forwards.
I disagree with everything you've said and implied and also I think you've entirely missed the point, when it comes to rating subgenres on a metal purity basis. All you're doing is making an argument for popularity disparity among the subgenres.
Not to mention Metallica aren't even that far removed from traditional heavy metal. Live in the future all you like, doesn't make your views more relevant than anybody else's of course, the fundamental objective point is that there is such a thing as metal purity and it has nothing to do with outsider reactions, popular opinion or a general distaste for foundational metal music.
I honestly can see their point too. Iron Maiden, Judas Priest, Black Sabbath are very classic rock radio station friendly compared to a lot of modern metal, or even 80's metal. There's nothing about that music that seems counter popular music culture, or even very heavy these days. It's as easy to listen to as like Led Zeppelin.
Ranking of each genre's overall metalness in order from most to least:
Trad metal
Power metal
Thrash metal = death metal
Doom metal
Groove metal
Non-prefixed black metal
Prog metal
Metalcore
Alternative metal = nu metal
Goth metal = folk metal
Prefixed black metal