It is true that as cities organically develop, things get more complicated. But planned cities have been built before, and they worked well for a very long time until they grew way beyond the intended size. Even after that, the planned portions still work pretty well. And lets face it: Most of our cities developed from very small settlements that were never intended to be gigantic cities. In the US it was even worse - most cities grew from very tiny, chaotic settlements like mining shanties, centers for early colonists etc, without any notable planning getting involved.
In history, a lot of societies including the Romans set up new, planned cities. A lot of these cities are major cities now, despite having grown way out of the scope the Romans could ever imagined. Yes, these cities also have big problems. But when they were laid out in 100 BC or 100 AD, nobody could ever imagine that they would grow to millions of people.
Today we know how big cities can grow, we know how to scope for them, and we can even build for such size. But its nearly impossible to revamp existing cities - it requires trillions of dollars due to property rights, and regulations even to start doing it, and the city must withstand immense disruption to everything.
But a new city can get around all of those because neither the incumbent interests, the real estate sector's overinflated properties etc nor the regulations and ordinances exist yet. It would be much easier to lay out a city.
And the bar is not high: Even if the new city can just start with a much better planned, already-built mass transportation and utility network, and could plan for green spaces from the start, it would be lightyears ahead of all existing cities.
And lets face it: Its much better for the trillions hoarded in imaginary numbers as wealth to be actually put into actual physical investments than sit inside the computerized financial system that makes money out of thin air. Solely starting building such a city would greatly stimulate the local and even state economies.
I actually wrote a piece about this without having heard of this new city project. I address these points and some more in that piece:
https://medium.com/@ozzeren/the-us-must-start-building-new-cities-24bffcaa3130
