The Internet has done a lot to help people “discover” previously unknown places. I’ve got a number of favorite parks and hiking trails near my house. Up until ten years ago, they were undiscovered and largely empty. Now the parking lots are always full and the trails crowded. Once I get past the one mile point, the trails empty out and generally at two or three miles you won’t see a soul.
The change in the past ten years has been huge.
As much as COVID is a major pain in the neck, our road traffic here on the San Francisco Peninsula is still down by two-thirds and maybe three-quarters. There aren’t as many insane drivers out. There are normally packed intersections here that used to take two or three light changes to get through. Now I’m often pulling up at the light as the first car. People seem to be taking life more slowly now.
While the beaches and parks near cities in my area are overrun on nice days, those in the mountains are similar to what you describe: Crowded roads and parking lots, but the further out you go, the less people you see. I find that hiking the old roads of the settlements that predated the parks are much more peaceful than the marked trail systems; no litter at all, or occasionally an old-fashioned bottle - you really get the impression that not a soul has been there in many decades (even if you can hear highway traffic in the distance).
I’ve also noticed an increase in stealth camping in those areas, and it is annoying - many first-timers who don’t bother to find a good spot but will literally put a small tent up right on a footpath. To their credit, they are neat and don’t litter. Years ago the rangers were aggressive in stopping this; I believe budget woes have reduced them to skeleton crews.
Generally backpacking has declined in this area (the NYC metro area); I attribute it to a population of “replacement Americans” who never participated in it (and don’t trust scout groups) coupled with fears of Lyme Disease.