IMO, places like Mackinac and Santa Catalina Islands, while maybe “totally” car free, though ultimately dependent on an automotive civilization, are destinations. Nice places to visit, though I would not want to live there.

My personal experiences with exciting and interesting places to live that are reasonably possible for a car-free (or at least car-lite) lifestyle, are Ann Arbor, MI and Boston, MA. I have visited Chicago, Washington, DC and NYC, and they seem possible too (though I am an urban, year-round cycle commuter, so weather and traffic are not deal-breakers for me).