I hesitate to make an all enveloping statement like "Rock is Dead," but it does seem to have been dying for a very long time. There has to be something new. People don't understand that when Rock and Roll first came out, it actually killed off other forms of popular music. The reason that doesn't happen now is that what is replacing rock is very diverse. Country. Hip Hop. Electronica. All of these could have been Rock's replacement, but they appeal to different people, and have their feet in rock anyway.
Rock, as a piece of our culture, shares some of the same attributes. Some of rock and metal is stuck in a time warp. You can't swing a dead cat without hitting a doom\stoner band that is trying so hard to sound like they are from the 70s that it hurts. However, there are still bands in that genre that are doing their own thing, as well as in other sub-genres.
Because US culture seems to have gotten stunted somewhere around 2000, of course you are going to see people looking backwards to something that is less complicated. There is an appeal to the 70s because it was before computers, before cell phones, before the huge political splintering, before globalization, before AIDS, before DARE, etc. That will be reflected in the "market" picking 70s wannabe bands.
Rock its self have become SO diverse that it is diluting its market share. Someone else mentioned this. As a consumer I can now dig into whatever rabbit hole niche I want. Its great for me, but it means there will never be a consensus again about something "everyone" likes. That means there can't be "rock gods." Not because performers now aren't that good, or ones in the past were that good, but because people's listening habits make such a confluence of opinions impossible.
Transversely, country, hip hop, EDM, jazz, etc aren't particularly diverse. A jazz or country album from 40 years ago could be remastered and released without anyone being the wiser. Hip Hop is a fairly young genre, and even though I'm no expert on it, I can hear the difference between music from the 80s, 90s, and 2000s. It is still in what I would call a box. Rock and metal have incorporated jazz, country, rap, and anything else into it at one time or another. Other genres rarely incorporate metal into their music because their fans\markets are too, for lack of a better word, weak to handle it.