> Cities are out of room

I don't think cities are actually out of room. Maybe they are, but it's not obvious to me that this is the case.

> Being able to share that growth with towns that have plenty of room to expand seems like a huge win.

Not for the people who live in smaller towns because they prefer living in smaller towns.

> And preventing people with money from coming to your poor town is an excellent way to make sure the people who live there stay poor.

Not all small towns are poor. And regardless, a lot of people with money coming into a town very often causes prices for everything (especially housing) to increase, pricing poor people out of the area. And if you're poor, you probably can't afford to move elsewhere.

Not saying that these problems are inevitable, but there are certainly lots of examples of them happening. What I am saying is that this is a very complicated thing with no clear outcome for any particular place.

I'm sure there are pluses and minuses for both options but what works in one place won't necessarily work the same in another. It can be a boon for the areas people are migrating to but you can easily get gentrification instead.

Different parts of US, Australia, or Europe will respond differently even when subjected to the same policy. So I don't think any one answer is correct as a general rule. But I am afraid in some places some will try to blindly replicate success stories from other places, with dire consequences.

> Cities are out of room and can only grow by increasing the commutes even more.

...or more effectively, by abandoning the flawed concept of single-family zoning, thereby allowing market forces to increase housing supply where it is needed.

You still end up with a ton of commuting needs. And you get an induced demand loop with development still: lots of jobs popped up in this area around the transit stops! Now more housing is built so people can live closer to it! Now even more commercial and retail is needed and gets built! Which makes even more people want to work/live there. And not all of those people are gonna want to both work and live there (consider the trivial case, even, of a couple with one job per person, with the jobs in different parts of town), so you've also increased your commuting demand, which means fuller trains, longer waits...

I've had coworkers who lived and worked in Beijing without cars - they still had 40+ minute each direction commutes. And that's a city that was extremely aggressive in expanding its transit. It's just a basic queuing/graph problem, though.

These all sound like good problems to have, relative to the current car-commuting sprawl mess, with its attendant CO2 and land use impacts.

But hard problems to convince people to want who are used to air conditioned private pods instead of hot cattlecars with groping and harrasment, if we're just picking the least attractive elements of each method. "An hour, but on your feet crammed like sardines with everyone else" will get even less appealing to someone used to the car-based life if self-driving cars ever take off.

If people only make cases for transit by straw-manning the worst part of cars and ignoring the worst part of mass transit it's gonna take a long time to convince enough people to spend the billions needed to make it happen, since most people aren't stupid and they know that there are cons of public transit too, not just unalloyed pros.