Overtourism of big destinations is not likely to end altogether, but the validity of their worth is premised on broader cultural narratives about what to venerate, what to be seen upholding, and that's bound to change as society does. In the past tourism served a purpose of exporting ideas about how to live: ideas about food, fashion, lifestyle could only truly be experienced by being there. Unusual merchandise could only be found where there was a center of trade. But as we live online more, exchange more of our goods by mail, a global city is, in effect, always with us, independent of the built infrastructure. And we hit a forcing function for moving in that direction by shutting down so much of the physical economy.
A park is on the affordable side compared to overseas travel, or plane travel in general, for many households.
There are already stories out there of people renting flats to use in Airbnb only.
While you have and had strict regulations on hotels and renting flats out, Airbnb just ignored it. What happened? Cheap rooms for Tourists, pushing rent prices higher, and putting a dent on hotels who have to have high standards and high investments.
International tourism and cruising may also lose their impact for social signalling. Both are at least partly motivated by the desire to come back and tell all your friends about where you were and what a wonderful time you had. The actual experience of having your pocket picked or being in a norovirus outbreak may not be all that great.
If you think the cruise ship stories were bad, those travellers at least had rooms and kitchens.
Airports don't have that.