It was all a sign of the times. For the younger people the late 80's and early 90's saw more drugs especially in the urban communities so the music reflected the hard times that drugs has on a community that was already poor and underfunded. Hell, a good number of grunge artists died because of drugs and many late 80's and early 90's rappers grew up around drugs.
As far as Nu Metal goes I think of bands like Limp Bizkit, Korn, etc. and I always consider that music an extension of music that hated but needed capitalism. Woodstock '99 (I think) was a good example of that where corporate was so greedy selling water and things like that at crazy prices that the event ended up being pretty bad.
The 90's was not all bad though imo. I think women artists really started coming into their own in the 90's. Concerts like Lilith Fair and it is not complete to talk about the 90's without women artists like Whitney Houston, Mariah Carey, Alanis Morrissette, Britney Spears, Sarah McLachlan, etc.
The 90's was also the last big decade for boy bands and more of an influx of international artists more than ever along with the niche acts too such as Hootie and The Blowfish, Matchbox 20, Dave Matthews Band, etc.