If you go to a place like Desolation Wilderness, one of the reasons they can keep it feeling like wilderness is by enforcing fairly strict rules on visitors. In particular, the rules around where you can hike, where you can camp, where you can start a fire, and what sorts of activities you can do there.

In areas where the government doesn't enforce so many rules, there will be recreational vehicles, hunting, logging, all sorts of other disruptive activities.

So ironically, the only places that can still feel like wilderness are the places where the government takes some action to keep it that way.