If we want a shift to walking, we need to either a) develop cities much more slowly and organically with a car prohibition (1800s simulator) or b) copy the layouts of cities that developed under a natural version of (a).

There is also another issue in the USA specifically, which is that certain people don't want to live around certain other people. This has driven a lot of the suburbanization in the USA AFAICT. I'm not sure what to do about it, exactly, but what's being done currently does not appear to be working.