I think he’s put forth a fairly accurate portrayal of the past, and possibly an accurate prediction of the future.
There can’t be another time period like 1958 to 1988 any more than there can be another first landing on the moon. Things happen during the passage of time that don’t ever occur again. That’s not hard to understand and quite easy to observe.
We all know that the most popular new artist in ‘65 remained popular a lot longer than the most popular artist in 2015. We all know it’s a little more difficult to play something new and innovative on an instrument 2021 than it was on the same instrument in 1969. These aren’t opinions, they are just events / conditions that can be observed.
Is Rock dead? It’s probably more accurate to say that Rock is no longer the type of music that dominates Pop music. It had a good 40+ year run, and it still exists, so it’s not dead. Discrimination by race, gender, sexual preference, religion, etc. is taboo around the world, but age discrimination is still widely accepted; just ask an old person. Rock is the music of the old.
Will it dominate Pop again? It’s not likely any specific type of music will dominate Pop going forward. It’s probably accurate to say there really isn’t any Pop music anymore, there’s just music of the moment, soon to be replaced by the music of the next moment & the replacement rate is accelerating.