My generation, the last of generation X, probably wanted to express existential angst with loud music such as altern rock and metal – music centered around distorted guitars. Metal took more hopeful '50s and '60s guitar music and turned it into darkness and despair, just like the hippie philosophy and in a way the general world view did.
The millennial generation – my younger brother – clearly follows a different path, more into electronics, going out, partying, and oriented towards the self. I feel they prefer to (comparatively) focus more their own little bubble and pleasure, and less scream about general misery or the state of the world.
I'm a guitar player and one of the last of generation X, and as an angry aggressive male I simply can't imagine hopping around on electronics as an outlet. I think guitar music and specifically heavy genres are far from dead – especially here in Northern Europe – but young(er) people have a different way of expressing and listening to music which is not very guitar-centric. They don't necessarily want to sit down and listen to a record full of doom music like us metalheads did/do, or at least, that's not the main way of enjoying music. It remains to be seen how much this pattern of music consumption will influence how people experience music in the long term.