It's not dead but it's definitely no longer the mainstream like it was at the height of Nirvana.

Thinking more about was pure rock n roll really ever the mainstream? Maybe in the 80s?

Rock festivals like rock am ring are still going strong. I think it's still very much alive and well but definitely overpowered by auto tune hip hop or techno pop music. The radio and music television isn't very good at representing rock anymore.