I know there are people in your generation that do have the ambition to put in the time and effort to learn to play guitar, bass, drums, or learn how to sing in a rock/,metal style so when I said millennial are lacking in ambition, I meant on average, as a whole. The types of music that you mentioned don't require the ambition and work ethic to become proficient in compared to the proficiency needed to play, for example, heavy metal guitar at a high level.
The types of music you mentioned being popular now instead of rock - pop, rap and electronic (we just called it dance or disco) are all things we had in my generation (graduated high school in 1986) but they are types of music that primarily girls would have been interested in. I don't see it as a genuine replacement for rock because it's what would have been called pussy music by most guys of my generation.
In my era we wanted to hear music that was played by competent musicians, guys who could really play their instrument well and the music usually had an air of rebellion to it, music that could be aggressive at times at least and that describes everything from the crunch of the guitar to the way the drums were hit. Yet at the same time you also had to be highly skilled, not just loud and aggressive but without any musical substance to it. There isn't a type of music doing well today that combines the musical proficiency and the aggression and energy of hard rock/metal of the 70s and 80s.
It's hard to believe there isn't still a huge market for rock. There just isn't a viable way to sell it now. It gets stolen and the laws aren't enforced. the government just looks the other way. It always thought roc music was subversive and felt threatened by it but never had a means of stopping it until the internet came along. The internet accomplished what the government would have liked to have done to rock but didn't know how to.
A musical style that was incredibly popular from the time it was invented in the 50s and then on through the 60s, 70s, 80s and 90s never should have died as sudden a death as rock did around the turn of the century. It was extremely unnatural for something that was consistently that popular for about 50 years to just suddenly die. Yet there hasn't been a single rock star to have made his debut in this century. The problem is the death of the industry itself. Not the art from but the means of marketing and selling it. The advent of the internet coincided perfectly with the death of the music industry. Any industry would die if its product suddenly started to be given away for free. There isn't an industry in existence that could survive something like that. Metallica tried to warn the fans about what would happen f these illegal sites were allowed to exist but people didn't listen. The greed of the fans to want the product of someone else's labor without paying and having parents who raised them so poorly that they thought they were actually entitled to have the product of someone else's labor for free killed rock 'n roll.