> Rowell is quick to note that by “we,” he means people over the age of 25, and that he’s focused on “the hold rock and pop music from the past has on us.”

Pop is timeless almost by definition, and rock music is pretty much dead. Beyond being the general trend, I'd bet one reason rap is ascendant is that it's so damn easy to get started - you don't need to gather up friends and buy instruments, everything can be done on your own with just a phone. Running a sequencer or a synthesizer doesn't require the kind of physical talent and training that playing musical instruments does. You don't need to have a great voice or vocal training to spit bars worth listening to.