I don't see the things like you.
The problem to fill the stadium is not a big band with something new. Metal is not the fashion in the world. Rock and metal were fashion at the end of seventy, to begining of ninety. So the called big bands were born in this years. They fill the stadiums cause a lot of people whom aren't in metal now go to the shows because is the music of their childhood or teenage. Today you can put a new band with an incredible new form to play and is not gonna fill. They will not be at radio or tv. How many new musicians can live today playing in a metal band? I meet some musicians playing in pop bands to pay the bills, and in his metal band to do what they like.
No fashion music, no people enough to fill the stadium. Pop and raeggeton (i don't know write it ok) music is the fashion. Is easy to hear, and the singer must be pretty, and nake please. The old glories of pop like Madonna or Michael Jackson has/had some really good songs. The new fashion singers no. Fast music for a fast consum.
But i really think metal will not die cause is the music of rebelliion against society, hypocrisy, religions, security forces and the rules. Goberments want all controlled, labeled and in lines. I hope always there are people against those things. Some of they will make and hear music, and a great part of this music will be metal

Something different in metal?
Djent is rellativament new, as genre.
Annal Nathrakh, less "The Codex Necros" that is black metal, the rest of the discography. The music is like an onion. When i understand a layer, there is a new one behind to investigate. Nerver will fill a stadium.
Hybernoid was a strange engish group from 94 to 96 with deat, doom, electronic an industrial mix in the music. Unknow for a big part of the metal community.