Youth is probably more of a function of responsibility and circumstance than it is age. I'm 24, I sometimes run with undergrads and they often seem really young - many of them don't cook for themselves and don't have anything outside of school and hobbies (they are stuck in what seems an eternal becoming). I remember telling my friend that I had to get my windshield replaced because it cracked and he thought it was like a 'real life thing', something that older and more responsible people would do but he certainly couldn't or wouldn't
Who am I to talk though - I'm a graduate student, sure I own a couch and I take my car in for oil changes and repairs but what real responsibilities do I have? I have a friend who has a wife, pets, and is looking for a house, he's certainly much older than the three years he has on me.
A lot of people fight 'getting old' because they are afraid of dying and the equate youth with life. They think that youth means a pursuit of novelty, of new experience, and that somehow by constantly experiencing new things they'll be youthful. They don't understand that this just makes them a tourist in life. Never settling down, never finding and making a place of your own. If you never really find a place of your own you leave it up to the city, the government, or whomever, this creates more administrative bloat.
I'm sure we all know those people who are constantly looking for 'new music' - I was more than definitely one of them at one point. They're tourists, they can name all the artists and albums they've listened to, they probably know a good 'harsh noise' band or two and probably some interesting post-rock, just like some people can show you pictures of all of the places they've visited. For the life of them, it would be hard to really listen to something and understand it. They have the appearance of understanding music without have really experienced it. They probably don't know the experience of keeping, say, 10 CDs in your car and listening to them over and over again, till the songs can be played forwards and backwards in their head. \
To some extent this is the problem with education - many universities require that students satisfy some breadth requirement. The spirit is right - people who want an education should be educated, not trained. When this education amounts to a cursory survey of, say, British Literature of the 1800s, US Civil Rights, and soil science (for, say, an engineer), it does little to develop real interests in students. The students then resent these things and continue their adolescent consumption habits. Never growing up to appreciate anything challenging or worthwhile. This is how you end up with YA fiction and Marvel dominating culture. This is how an abundance of online 'subcultures' become greater homes to people than their geographic locales.
Tourism ruins the world - it exploits local communities and makes them dependent on wealthy foreigners. Tourism creates things like Spotify, where media can be consumed more or less for the sake of consumption and people don't bother to know how it's created. Tourism creates a world where people don't own anything, lest they not be able to fit it in their suitcase. Tourism ruins culture, by causing people to never develop real taste or interests. Tourism is not itself a great evil, it's an amalgamation of forces - atomization of society, unchecked globalization, and a narcissistic culture that create one easily identifiable trait.