I'd say around the 1990s...
Because sampling became a huge thing and artists of that generation lacked creativity and they kept relying on old music of the 70s, they no longer played instruments, you could become a singer without having to actually sing, Soundscan became a huge culprit (basically it was all about how much you can sell within 1 week and it was no longer about your artistry).
The majority of the genres were no longer at it's peak. E.g. R&B, when rappers got involved with R&B music, sampling, the lyrical content was literally just about bedroom music and nothing more anymore.
Rock music. It was all about noise and lack of guitar riff raffs and grunge literally copied everything that 70s rock did and all grunge music was about was men crying about how miserable their lives were and they wanted to kill themselves.
There was exactly a brand name that represented their decades (even David Bowie said this)
Many more I can list.
What about you ?