Dyonisius, I've been listening metal since I can remember (My mother used to listen Judas priest, Black Sabbath, Iron Maiden, among other metal bands, I also grew up listening to Pink Floyd)
I grew up also with bands like Slayer, Bathory, Sarcofago, Hellhammer, Morbid Angel, etc.
Then, at the beginning of the 90's discovered Black metal in which I felt in love.
I listened to bands like Dark Throne, Emperor, Mayhem, Abruptum, Hades, Burzum, etc, there's so many bands I've been listening too.
Also I listen funeral doom bands like Thergothon, Disembowelment, Skepticism, Tyranny.
Now, The stagnation started longtime ago, even among heavy metal bands, but nowadays is quite more difficult to avoid. Let's face it, when Emperor released Anthem to the Welkin' at Dusk, Metal wasn't as so mainstream as it is now, For instance, bands like Dragonforce weren't making albums every week, And happily bands like Dimmu Borgir were releasing a few albums only.
Now, don't put the fault on Emperor only. Don't forget Cradle of Shit, and those shitty Gothic love songs. That was clearly bad, because it showed that metal could be somehow pop, And what about The Abyss? And Mr. Peter Tägtgren and his part of fault as well.
Decay started years ago, but didn't aggravate until a few years ago. I didn't state this before because and SIMPLY because I wasn't part of this forum before.