Rock is no longer a "mainstream" genre, in the sense that rock acts generally don't top the charts or occupy a large space in the zeitgeist (hip hop has replaced rock in this area). But I think this has been healthy for rock; the genre is now more fractured, and as a result, more varied and experimental. (Don't @ me metalheads. I love metal too but it is not a mainstream genre)
Sorry if that got a bit rambly -- just wanted to point out that there is tons of evolution in contemporary music. It can be harder to see that, though, since music streaming has taken a big chunk out of the music monoculture. That means finding interesting music is more accessible, but requires individual effort to seek out (and the sheer quantity can be overwhelming).
Here is an eclectic list of example metal bands from the last decade:
Diablo Swing Orchestra
The Hu
Finntroll
Baby Metal
Sumo Cyco
Archspire
Igorrr