If you look at Taylor Swift's first 12 number one hits, each of them was written by a different writer. Compare that to bands from 30 years ago, many of whom wrote and recorded all the songs themselves.
Labels don't sign rock bands anymore because actually recording a rock band well in a studio is 10x the cost of just using a sampler and a single artist singing. I know folks want to blame AI, but it's really just enabling the latest iteration of this trend.
I'm not defending the whole thing. It's a shame, and I love going back and listening to my old Rush albums. But AI is not the problem here. It's the incentives.