Surely rock is a limited, highly stylised form that has been heavily promoted over the last few decades.

Oh well, here we go: define "rock". No easier than defining "folk", is my guess.

No music is a "waste of time". Whether you like it or not is just personal taste. If it has validity for someone, it's not wasting their time. I like bits of Bob Dylan, Steeleye Span, Fairport Convention, Martin Carthy, Lindisfarne, Davy Graham, Bert Jansch, Dave Swarbrick, Anne Briggs, June Tabor, Cream, the McPeake Family... blah, blah, blah...