I agree it would be an improvement for people but a somewhat utopian one. But how do you figure we will do it?

Are your factoring in a drastic population decrease?

If you flatten out all tall buildings that house XX or XXX apartments you will a lot more space for the city. Which means the cost of rail, trains and a lot of service will increase.

It may be a lot like the suburbs, but with the houses closer and shared green space?

Is the garden meant to provide food for the people living there? If so who is doing the farming? A return to an agrarian society?

I would love to end factory farming, but is not a feasible option to feed as many people as we do today. Which again would be solved be a massiv reduction in the population.