The generational shift isn't between people, but between decades. Many of the "leave no trace" hikers today were very different in their youth. Look through the history and you will find people in the 60s regularly doing things that today are simply not allowed (fires, cutting down small trees etc). So it isn't that people are different today. There are just more of them on trails.

Some would say the answer is to provide more services such as better camping accommodations and harder trail surfaces to handle the extra people. I do not support this. I suggest that making trails easier attracts more people, only exacerbating the problem. It's a game that cannot be won.

So rather than try to accommodate all these people, perhaps parts of the trail should be made less accommodating. Rock climbers do this all the time. See debates over sport (heavily bolted) v. traditional climbing methods. Adding safety features to a route attracts more traffic. Making/keeping a route difficult or even dangerous keeps beginners away, which reduces traffic. If we assume that there will always be more people in the future than there are now, that if nothing changes population pressure will always increase, then actively trying to keep people away may be the only sustainable plan.