Sklashboombash said it best earlier in this thread where it was mentioned that rock music is cyclical and when it comes back it has to come back but at a slightly different angle. (Thus contributing to the generational gap) This is clearly true as late 60's rock artists sound nothing like mid 50's era rock n' roll; and we see rock clearly evolve, spread out, and touch new territory through the 70's, 80's, 90's, etc... We can hear the differences in 70's rock vs 80's new wave and 80's hair metal vs 90's grunge/post grunge. Despite the differences in styles what these all have in common is they are all music created with guitar, bass, drums, and in some cases some kind of keys/synths.
From the 50s through the 90s there were only so many radio stations, only so many tv channels to watch. Therefore people tended to listen to/watch a lot of the same things and could relate based on that. Remember when you went to work/school in the 90s and you stood around in a group of say 10 people and said "did you catch Seinfeld last night?" Chances are most of the others watched the same thing you did simply because there weren't that many tv channels to choose from, even with cable. Now, cable is 700+ channels, and it competes with so much additional content from Netflix, Apple TV, Amazon, YouTube, etc. In 2018 if you stood in the same group of 10 people and asked if they caught a particular show last night, most likely no one would have seen the same thing. This is because we have so many choices today.
The same thing applies to music. From the 50's through the 90's, AM and eventually FM radio were a big deal and that's where everyone heard their tunes. Therefore a lot of people liked the same music. You'd hear the tunes, go to the record store to buy the 45 or the album, eventually cassette or cd, and maybe put down a couple bucks to see an artist in concert. The radio was a huge center of the music universe for over 40+ years. All the rock artists being promoted to the masses were found in one place with the radio. Eventually MTV comes along and provides a second place for people to follow these said artists. Again, these media outlets were the center of the rock music universe. With everyone tuning into these said media outlets this is how the older artists sold tons of records and built followings large enough to fill big stadiums. There were fewer artists being pushed to the masses which meant the ones who did make it were exposed to huge numbers of people.
Today it's very different. There's a zillion artists with a zillion different media outlets, all fighting for your attention. With the radio mostly taken out of the equation and an MTV that doesn't play videos there isn't that center of the universe for rock music anymore that there once was. Therefore bands aren't being exposed to people in the numbers they once were. Everyone kind of goes in their own direction. Bands keep you updated on their individual happenings via the internet and it's up to you to keep up with it on your own.
So to sum it up, for almost 50 years, each time rock came back around at a different angle it had that "center of the universe" promoting it to the masses. It hasn't had that in arguably about 15 years now. So is this the reason it hasn't come back? Is it simply because the numbers aren't there? Is it because the exposure it once had no longer exists?
Btw... I had never actually listened to Greta Van Fleet until you guys brought it up yesterday. I can clearly see the intergenerational appeal, but that's simply because they are a contemporary band who are going for the 70's sound and their singer sounds EXACTLY like Robert Plant. Not to be dismissive of their music, but I see them as just a throwback. These guys aren't changing music or bringing back rock. They're satisfying someone's desire for new music from Robert Plant. They sound like a Zeppelin tribute band who decided to write a few of their own tunes. Music is all about what moves you though and if these guys move you then hey, more power to you.
As for Westenn's comment, I think your observation is interesting, but as for women who are trying to rock... some women don't need to try to rock, they just are rock. Donita Sparks IS rock. With the exception of Frances Bean, the women you cited are all pop stars who are trying to break the mold of their created image by piggybacking on established older rock acts. They're no different than say Debbie Gibson or Tiffany. Created pop acts who are cast into a role. Those tv shows you mentioned are the devil of the modern era music industry and definitely do a lot to dumb things down to the lowest common denominator. I am not a fan. I'm interested though, what is it about Lady Gaga's movie that you feel will change music?