Cars are the most sensitive form of transport to both traffic and parking, and even then the only other form of transport I can think of where parking is an issue is biking. If you could walk or take public transit, there would be no need to park, and traffic would be much lower because much less space is needed per commuter. Wider roads and more parking spaces are easy to point to as solutions but the real problem is subpar, uncomfortable, or even non-existent public transportation.

> but then they might not be economically viable

I want a source for this. I've never been to Tokyo or Amsterdam, but everyone I know who's been there describe the zoning working exactly this way and it seems economically viable.