Not everywhere. When I was in school in Boston, I went everywhere by public transit. I never missed having a car (I rented one the few times I wanted to travel somewhere like up to New Hampshire to see foliage). However, I also learned from that experience that I don't want to live in a place like that for the rest of my life.

not every city with great transit has to be a stressful megalopolis like NYC - Vienna or Zurich for example are really nice and quiet (and clean and have low crime) despite having great transit

I didn't find Boston to be a "stressful megalopolis" (I haven't lived in NYC so I can't speak to that). I just realized I didn't want to live permanently in a place that dense. I've also visited London and Paris, both of which have excellent mass transit (at least by US standards), and while I enjoyed visiting them, I don't think I would want to live permanently in those cities either. Maybe I'll get a chance sometime to visit one of the smaller European cities you mention to see what they're like.