Try Yellowstone in the summer if you want ruined. Non-stop traffic jams, trash everywhere, random punk kids carving crap into every tree on a path they meet, and nearly every tree seems to have carvings scraped off it multiple times.
Why? There are millions of places to visit, the vast majority of which are nearly empty. You don't have to go to the big name locations, there are plenty of others that aren't crowded.
Yeah. Much of the 'real world' is turning into something like a Center Parks (if you know of it) experience, where what we believe to be reality is nothing of the sort. At least some trips are immune though, like a tropical chill out on the beach. It's the long dreamed of trip to Florence, for example, that is likely to be marred.
This comment made me realise why this thread gave me an uneasy feeling. It's not being upset about people travelling, it's being upset about the wrong people travelling for the wrong reasons. I don't see why your long-dreamed of trip is more virtuous than one someone chose because they saw a nice picture on social media.