What I want more than a car-less city, is a city that properly separates out walkability from drivability. Use the superblock approach, but mandate all buildings have to be the same height and are connected to a public skyway network like so: https://i.imgur.com/hYGpQp4.png
You can make these roofs a proper public space rather than just being unused as they are today, and you don't have to worry about crosswalks / mixed pedestrian + car usage for roads.
This exists in places like Calgary (+15 Skywalk) and Edmonton (Pedways), and underground in places like Toronto (PATH) and Montréal (RÉSO) to try and separate pedestrians from snow and being sprayed by slush from cars.
From a weather perspective, they're pretty nice in the winter, but they suffer from a number of problems such as weird hours, lack of step free access, and fundamentally removing you from the urban fabric of the city. Oh, and they meander everywhere so it often takes a lot longer to use them. You end up with odd liminal spaces that can sometimes feel quite dangerous.
It has been tried, but it quickly turns into a dystopian hellscape. If you don't have people on the streets they turn into crime dens. Meanwhile, the skywalks are not visible from the buildings so they lack social control - and are completely unreachable for emergency services. Not to mention that the main benefit of pedestrian areas is the wide-open spaces connected to a dense network of local infrastructure, which such a skywalk would not provide.
The only way this works is by separating out the cars - like highways are doing. Due to the lack of physical space to exist and the huge speed difference they are completely incompatible with non-car traffic.
There's a neighborhood in Helsinki that's built like that called East Pasila. Most people hate it. Its constantly rated as one of the least desirable districts in the city.
You could probably get even better walk-able integration by connecting together multiple floors worth of hallways, one above the other. That could approach a 3D city a little bit more.
You can make these roofs a proper public space rather than just being unused as they are today, and you don't have to worry about crosswalks / mixed pedestrian + car usage for roads.