From what I can gather, a large number of people here actually hate '90s mainstream music primarily because they have elected to despise the entirety of nearly every genre of music. This would generally cut down your appreciation of nearly every decade, especially the ones in which you have lived; many people find that "70s music was better" now because they may pick and choose what of that music they listen to, more. There are a large number of bands in any era, and many who cherish the '70s rock scene neglect the very large amount of terrible music created during that decade. I mean, for those lambasting dance and techno, how do you defend the large record sales of disco during the '70s as any better? If you choose to only listen to music in the genres you like from Decade A, but grew up in Decade B, thereby hearing by chance on the airwaves music of all its genres, you will prefer Decade A because of your artifically narrowed sample size.

I happen to like a lot of music made in the '90s. I don't know in relevance to other decades, as I do not, (in contrast, evidently, to many), make elaborate charts of what percentage of a decade's music I like based on Network Theory. Much of what became the indie scene, notably, exploded, as did the Finnish popular music scene along with the Scandanavian scene in general.

Was Black Metal a '90s creation, though? If so, that was pretty unfortunate, if taken seriously. Ah, Mayhem, such ridiculousness as yours I have never known.