Isn't Venice as problematic/artificial as suburbia in its own way? If you're saying car-free then I assume you mean the centre, where the real population is tiny (compared to San Francisco at <50k), aging, declining amd dwarfed by tourists. My understanding is that it's increasingly meeting needs of tens of millions of ultra short term visitors rather than real communities. It feels like there must be a wide range of happy medium places in between.