Mainstream rock has always been formulaic whether it was glam, hair metal, grunge, emo or anything else popular. If you want interesting music in any genre you have to look on the fringes where bands priorities are more likely to be creativity rather than radio friendly unit shifting. Occasionally one of those fringe bands breaks through to the mainstream (Idles for example) but it's rare.
Same goes for festivals. If you want a great atmosphere and interesting music, head for one of the smaller ones where they book bands they like instead of bands who sell tickets.
I used to go to Glastonbury every year but now I'd rather go to a small genre specific festival, pay a quarter of the ticket price, see better bands and drink better beer and enjoy a better atmosphere