You're mistaking what you like, with what young people like.
I'd rather hear Pink Floyd than Billie Eilish. But I recognise that festival headliners have to be more youth oriented.
Glastonbury is actually pretty good at catering to everyone though, Eilish on the Friday for young pop, McCartney on the Saturday for classic rock and Lamar on the Sunday for hip hop. That seems a fair mix to me and there are plenty of other stages if those headliners don't appeal.