Not the person you're referring to, but I'll take a crack at it
The one of the issues is a complete lack of suitable soil to grow all the stuff that's in the diagram. Soil was stripped and compacted to create a parking lot.
You have to break up the pavement, haul it all out, and take it to a recycler or Landfill.
There is a lot of planning of where things go, how big they will be.
We have a pond so we have to design that
It also takes time for trees to grow to the size we want them
Money. Nobody would ever foot the bill for this and even then, it would take a significant amount of overhead to keep it running. Also, you're never going to convince people to use public transportation. That's just a few things. My point is this is represented as a utopia but it could never exist. Not in the nations current state. The ideal is good in practice but it's getting there that's the issue.