This even affects Mount Everest where people are literally dying just to say they stood at the top of the world. And Everest simply can't support the number of climbers now.
You see this in US national parks where the obvious ones (eg Yosemite) are arguably oversubscribed while others you could probably go days without seeing anyone.
There's a certain lack of imagination here. Some of it is convenience. Take Everest. People climb it because it's the tallest and people know what it is. There are ~14 other peaks over 8000 meters. Are any of these qualitatively worse experiences? Probably not. But... bragging rights.
Solutions to this fall into a number of buckets:
1. Making it more expensive: some will complain only the rich can go and this is unfair.
2. Quotas: you have to book far, far in advance and no doubt this is unfair to some people.
3. Lottery system: this is really a variation of quotas but probably fairer.
So I've been to Paris like 4 times. I like it but my God the touristy places are a nightmare such that I basically never went to any. Honestly the best part for me was the bread. The sandwiches you'd buy on the street were unbelievably good.
Anyway, I honestly don't understand this need people have to jam in with 100,000 other people just to see some famous building. Maybe that's just me.