The big city that is also pleasant to live in

However

“It’s possible to have a liveable city at any scale—Tokyo proves that” could be challenged.

It’s certainly true for some values of “livable”, and may be possible if you are working within an old, well-established, stable, sustainable culture, like the island culture of Japan. Let’s see how that works in, say, Africa.

But some folks wouldn’t define any city “livable” that denies many/most of their residents a reasonable plot (maybe 100 sq m) of open land to go with their non-rabbit-hutch (200 sq m) personal housing. Privately held land…tragedy of the commons and all that.

Any high-density city seems like a devolutionary step from the lifestyles of our nomadic and pastoral ancestors who had such land (and whatever housing size they chose within their practical time and resource limits) as their birthright…

appreciation for the often discussed japanese zoning system http://urbankchoze.blogspot.com/2014/04/japanese-zoning.html