I was thinking about this the other day. If I had half a trillion dollars (like the guy who just bought the presidency) I would spend it building a city from scratch. A walkable/bikeable city with free public transportation. I don’t have enough expertise to speak about affordable housing ideas, but with that amount of money I can pay someone to come up with some good regulations. Don’t know why but that’d be my passion project.
I agree with you, that would be a much more effective use of resources. It’s a fantasy though, and it’s way more fun for me to daydream about design than manipulating public policy.
All that said it’s not a fruitless endeavor to think about how you would build something from scratch even if you can’t. It is a good way to hash out ideas without getting bogged down by the resistance to change.