When you say "low quality building on large sections in a vast area" that makes me think of American style restrictive single-family zoning. And hey, looks like they had something similar until last year:
https://www.theguardian.com/world/2021/dec/15/new-zealand-ha...>Planning law has long been criticised for being restrictive, unwieldy and slow. It is blamed in part for slowing down housing development, entrenching single-house dwellings, and creating urban sprawl, which has implications for transport, infrastructure and climate change.
>Building a standard single-story house in New Zealand comes with a lot of paperwork, but trying to build a multi-storey or multi-dwelling development could tie someone up in regulatory battles for months or years, at great expense.
>If an area is zoned as a single-family area, the standard residence is a single house with a garden. Anyone wanting to build multiple dwellings, or anything other than a standard house, requires consent from the local council. Councils can reject the application for a whole number of reasons, including, for example, an unhappy neighbour about to lose some sunlight.
So it just proves my point even more. Left to their own devices, people do not naturally make nothing but low density low quality suburbia. It didn't exist until government zoning was introduced after WW2. Same thing happens here: the Deanobox is a product of a restrictive planning regime.
If you really want to see what happens when people are allowed to build, look at Tokyo. A first world megalopolis, that is also affordable. They understand the revolutionary idea that homebuilding has to keep pace with the growth in residents.