The channel this video is from is out of this world. It redefined how I think about the cities and towns we live in and what is the objectively correct way to build them - with waaaaay more mixed use walkable residential.
The existing pre-war walkable neighborhoods are all we are going to get and they are expensive. We made walking to school a thing for rich kids.
It may not be sustainable for them, but it doesn't seem to be subsidized by the larger city tens of miles away.
To add, a lot of the economic activities in downtown areas are by workers and customers who live in the suburbs and commute into town. I don't believe that was taken into account.
The basic problem is density and scaling of infrastructure and utilities. The cost of many utilities (power, water, roads) is dominated by the distance from the source to the hookup. When buildings only scale laterally (single story) then comparatively more utilities are needed than when they can scale vertically into the 3rd dimension. This gets exaggerated because the population of a volume tends to scale much faster vertically than laterally (apartments are much closer together than single family dwellings) so most of the utility cost ends up being the lateral footprint of a neighborhood.
Looking at this another way, the taxes of lateral neighborhoods would need to grow exponentially faster than those in vertical neighborhoods to maintain the same unit of infrastructure.
Of course, I live in a walkable neighbourhood in Europe, so it’s easy for me to say that.