you have to become a city dweller on your little city island.
I don't understand the logic of your comment. First, in regards to commuting - for one thing, a car is not that large of a range extender. For day-to-day commutes, you are still on an island - just one that is defined by traffic congestion and proximity to highways rather than a public transit network. Perhaps it is different in Europe, but in many major US cities it is prohibitively expensive and time-consuming to use your car to commute in to the city center from the suburbs.
If you aren't talking about commuting, then you would need to willfully ignore rental cars (including car sharing). I don't know if you have something like Zipcar, but you just use the app on your phone to find an available car and take it - I can't believe that is such a burdensome amount of planning. When we lived in NYC, we would "spontaneously" take the Zipcar to see friends in New Jersey, or to hit the Target, or whatever. In addition, it was parked in a garage a lot closer than where we would be able to afford to keep a car.
Finally, it sounds like you are a lot more encumbered than you seem to think. You feel stuck where you are because of your ties to friends and family. In contrast, a single city dweller in a rented apartment is pretty free to move wherever opportunity arises. Which one of you is stuck on an "island"? I'm not judging your choices - whatever makes you happy. Like I said, I'm now married, have kids, I'm suburban, and we have 2 cars. But you are writing off a whole idea based on your own narrow experience.