> the solution there is increased density

This is a common narrative but no, it's not a viable solution except in the short term, witch means a way too costly solution in the mean and long term. Intermixing homes, restaurants, schools, shops, yes it's a MUST, yes, it's why here in EU spread areas works well even today, but not density.

Take as an example the classic paper mail: any condo have a dedicate area with a wall of mailboxes, a wonderful dense solution, anyone get the mail, the postman have a very shorter trip to delivery them. Ah, yes, they do not work much for parcels but BACK THEN parcels was very rare and mails very common. After a bit of time on-line retail flourish while mails became emails. In dense city, EU level density, it's a nightmare. First delivery vehicles need to be bigger and there is no place for them to stop and deliver, delivery to single home can be quick enough for a stop&go but for a condo where you might have 5-8 parcels and the delivery man it's not alone, another have also some parcels to deliver in the very same place at the very same time it's a big issue. It's an even bigger issue inside: the mailbox area is just a wall, there is no room for enough space for parcels, so it's next to impossible delivering them in a common place in an already built condo. Few might be adapted but most simply can't. Single family homes with a bit of ground around on contrary have no issues, switching from a small mailbox to a bigger parcel box is just a matter of cutting a bit more fence and insert the new "big box". It's a very simple change in society and dense cities can't adapt. Drone delivery? Try to imaging a flying drone delivering to a balcony in a condo, it's can't work, while there is not much issues having on the same big parcel box a "special" roof for drone delivery with a very visible address mark for them. Flying cars? Well, if you have a garden adapting a place for landing it's not really an issue, in a dense city? I'm curious those who have written https://www.easa.europa.eu/sites/default/files/dfu/uam-full-... what they have in their head... Even if we had eVTOLs today they are ALL but urban. They would be a perfect match for a spread area where there is room for take off and landing, and the quick run by air help to be "dense" while being spread. Back to today just see how much metros costs and how limited they are, how many parking issue, how impossible is to convert multi-storey buildings to the Green New Deal: no room for enough p.v., no root for proper heat-pump heating and so on.

Long story short: a dense city is like a factory, very effective wen you live inside during the period it was designed for, a nightmare when things change. A nightmare to change it to adapt. That's why today thanks to modern logistic and remote work we can achieve city-like efficiency without being dense, the new right density for the economy of scale is a spread population living and working in small buildings, intermixed, not too spread, but with enough space around to change them completely, to being able to evolve at the minimum cost and maximum flexibility. That's is not advertised, even denied, because is such a society git economy can't exists. There is no room for ready-made food in a spread population where WFH is the norm for all eligible jobs, there is no room for Uber et al. for cars, there is no room for public laundry and other service, such spread society know the value of ownership and instead of owning nothing living like slaves at the mercy of few paying the slaves just the bare minimum to allow them pay services they needs to live, enough to avoid riots and revolutions, it's a society like the classic desktop model of individual interconnected and in full control of themselves, moving in a peer to peer society.

Not try looking at modern cities, from Neom to Arkadag, Innopolis, Prospera etc, they are distopic realities where people are slaves AND they cost so much that's impossible to create smart cities for all.