Lower density is expensive. You're spreading out infrastructure costs to less households and businesses, increasing commute times (sure, cars are faster than the bus, but in urban areas is usually the same speed as the subway and walking and cycling), and generally taking up a larger environmental footprint.

Of course I don't want to live in Hong Kong or Singapore core, that's way too crammed. But if we look at Tokyo, which is second in urban development size only to NYC, and is the same size as the state of Connecticut, their population density is not high at all. 200-400 US cities would have higher population density than the Greater Tokyo Area.

Correct me if I'm wrong, but what you want is a medium density, larger urban area kinda like Greater Tokyo or NYC, with everyone free to drive wherever they want with manageable traffic.

This exists in reality, except car ownership is pretty low for Tokyo, and in NYC's car ownership is mostly centred in the suburbs. https://edc.nyc/article/new-yorkers-and-their-cars

So when people are free to choose, only 10-40% of households in your ideal metro area (can't say city cause it's too sparse) choose car ownership. That's not out of poverty, Tokyo and NYC are among the highest earning cities in the world.

What makes those two cities livable and world-class is the public transit that connects the various boroughs together. NYC needs to improve in this regard because they don't have a ring line yet, but Tokyo is pretty good at it. I also picked two random spots in Tokyo, and though car is faster by 10 minutes when it's quiet, it's an hour slower if there's traffic.

The Greater Toronto Area is an example of what happens when you have a medium density, large metro area without good inter-borough public transit (and mediocre intra-borough PT outside of Toronto proper). You have all the high costs of urban living (you gotta pay for each borough's budgets as a separate city, as well as the huge road infrastructure costs) with few of the benefits (suburbs are isolated, you get this very Americanized feel of restrictive zoning and stroads, etc).

You can't pick and choose what aspects of our reality to address; the current price of Self-Driving (nevermind it's not SAE Level 5 yet) matters because it's real life. Just because the topic is Singularitarianism doesn't mean we are allowed to toss money and resource scarcity out the window. Or else I can say hey, singularity, cities won't be necessary anymore because we can live in underground pods and interact in Web 5.0.