> The concepts of the city and the condominium aren’t going anywhere though

I'm not sure of that, at all: I see the green new deal as something happening that's here to last, and I see no chances to "migrate" to green new deal condos, electrifying them on scale. Yes, you can build a NEW condo "A class, all electric", but there is no chances to transform those built decades ago, and no chances to re-built them as well. Yes, in temperate climate it's still doable to put an air-water heating powerful enough per unit, even a central heating. However the operational cost of such move will be FAR higher than gas at actual prices, not only, if ALL condos switch to such heating setup we simply can't provide enough electricity for them all.

Where I'm from (north-west Italy, so not a cold region) a classic apartment have circa 24kW thermal gas or oil heating system. Converted to an air-water heat pump it would be around 6-8kW normal absorption for 6 hours per day at least 4-5 month per year. With ALL units at 6-8kW + the rest there is simply no generation capacity. No chance to electrify. Meanwhile where I'm now, in a much fresh place in winter, 1kW heat a home far bigger than a typical apartment most of the year, with -25℃ outside 4kW suffice. At this absorption rate there is enough generation capacity to be all electric. That's why we need new buildings.

Now HOW to made them? In a dense city crushing and rebuilt a condo is hardly feasible, in EU anything was designed at a walk distance, crushing a condo means blocking roads nearby for some months, there is simply no space to do so without big issues. It could be done for ONE condo, definitively not en-masse. Single family homes on contrary are easier to rebuilt end generally have enough space around to put a construction site in place without dramas. Aside we have many cities in places more and more flooded, subjected to dangerous subsidence and so on, again we can't rebuild cities, it's simply too costly. Take a look at the Indian's 100-smart city program, where the ENTIRE COUNTRY resources would be needed to built 100 cities able theoretically to host only a very limited percentage of population.

Long story short: modern city, future cities are like the ancient Fordlandia from Henry Ford, equally a failure and a distopic nightmare.

> Cities have existed for as long as written history has. They can only get so wide before there’s pressure to build up. What’s the alternative?

Yes, because we never have had current TLC/IT and logistics. Today it's cheaper to build a chair in China, with wood from Poland, straw seat from Brazil, metallic connectors from India to sell it in Canada than directly build it in Canada few kilometers away of the final customer. We are in a changing world and that means mass migrations, war, we need flexibility to relocate and cope with countless "whole country malfunctioning issues" for a long period of time, in a city it's a nightmare, anyone eat, but all the food came from elsewhere, big infra are need to move food, goods in general, there is little to no room to change, an easy target for bombing during a war, an easy target to spread diseases and so on. The alternative is living in less dense and more geographically distributed ways, so we can relocate easily because number of people to move per single area on earth are not so high, impacted people from extreme weather, war, crisis events far more manageable, there is room for limited autonomy to be resilient, there is space to evolve as the tech change.

> Vanishingly few people have the financial privilege to buy, let alone build, anywhere near a city, I’m sure you’re aware.

Ignore the current economy: can we MATERIALLY build single family home for almost anyone? In terms of industrial output ability, raw materials availability and so on? I think yes in all western countries and in many other as well. Economy it's just a measure. If we, the people, decide to do something doable materially, the economy will change to make it possible, because the current economic state of things is the byproduct of the current failing democratic model, we are in a kind of economic dictatorship modeled after/well described by the ancient pamphlet The Science Of Government, Founded On Natural Law, by Clinton Roosevelt. If we decide to change our countries without the need of a III world war we can. 99% can. If most prefer stop the history train they will fails as regularly happen in history, ending up in city more and more similar to ghettos with a lower and lower mean income, bigger and bigger criminal activities, desperation and so on, as you can already observe in most USA big and medium cities compared to themselves 20+ years ago. As you can see in most EU cities even if at a slower rate than the USA simply because we have much more social protections that slow down the economical effects of current policies.

> There simply isn’t a world where every single person can live in a PV-powered, water tank backed up fortress, with ample setbacks to keep your neighbours away. That’s far more dystopian to me than any “you’ll never own anything” boogeyman.

There is no need to keep our neighbors away IF we slowly change from the city model to the spread model with public investments starting from WFH as a key element to allow people flee the city and behind them paving the way for others to build services outside "now" that there is a market outside. It's a path doable an year after another with a significant economy boost form such enormous general relocation effort.