So OP is referring to really large cities.
In our region for that, world class San Francisco is dramatically unlike any other city in California. Potentially very exciting fun place for any gregarious person, especially those wealthy enough to afford it, with stunning natural beauty, marine cool, often foggy. I visit The City occasionally, usually for music events or exercise, but have only experienced a few of the reasons most tourists visit so would be a poor guide. If I had wealth, would like to have a part time small residence about the western or north side of the city where one can look out across residential zones sloping down towards the distant blue Pacific or bay. Reality is as a very desirable place, it is of course very expensive.
Well as a landscape photographer, Tahoe snow skier, and Sierra Nevada backpacker, I've gotten plenty of nature all my adult life. Could easily enjoy several months living slowly, quietly, simply, absorbing the essence of some places I've been. But there would be a time I'd feel a desire for other humans and civilization. My life has always been more than just about nature. Can drive from my urban world to world class scenic places within hours.
I live in an older 1970s era community of 300 separate 2-story 4-plexes within an upscale suburban Santa Clara County (2+ million population) mixed retail, commercial, and residential district. Lots of traffic, urban noise, endless ongoing construction, large retail chain stores, myriad amusements for an active frugal senior. A good place for this old counterculture person to safely hide out. But living here is very different than San Francisco, a very dense city where people use public transportation. Here within a mile of my residence it's automobile land suburban American, with banks, churches, gas stations, auto repair shops, alcohol bars, restaurants, theaters, supermarkets, Subways, Starbucks, Burger King, MacDonald's, Jack-n-the-Box, 7-11's, Walgreens, Home Depot, Office Depot, Arco, Kohl's, and much more.
Although I have a regional Clipper (senior subsidized cheap) transit pass and sometimes use it, I tend to drive my old dirty vehicle all over like a day base station. Bus stops are common about nearby streets. A Light Rail station is a 2/3 mile walk from which I can reach all areas of the region including San Francisco. Since late spring have done 11 regional outdoor street art/food/music festivals and 3 large venue rock concerts. Here within this large urban zone, there are endless ways for one to be absorbed by human culture of one's choice.
Then again, there are myriad people here in the South Bay and in San Francisco that live simple limited lives, ignored by others, mostly alone thus socially isolated, while merely being near others.