Another fix: remote work for all who can. No more traffic, no more living close to economic centers (expensive housing), leaves a lot of available housing in the cities (no more homelessness).
I understand what's trying to be said here but I'd pass on that.
I've lived in apartments most my life. Now that I live in a home that has a backyard, a garage, can't hear what my neighbors are saying, don't need to pay for laundry, don't need to go down an elevator to throw away garbage, and don't have to worry about people pissing in the elevator. I'm not going back to an apartment.
The only thing I don't see is how it would fix people being homeless. Many homeless are unable to be properly housed because they have mental illnesses, trauma, etc. If you put them in an apartment without extensive further help, many will get back on the street and/or destroy the apartment. You can't solve their problems with just providing housing.
I don't understand how the high density housing solves traffic. In lieu of an additional solution (public transit) I think it would make traffic worse.
Edit
The argument seems to be: high density housing would naturally result in public transit infrastructure. I don't think that line of reasoning makes sense, it's certainly not an obvious inevitability that public transit will always, naturally appear.
That could alleviate those problems, but I doubt it'd actually solve them. Not to mention, they could also get worse:
Cost of living -> Could actually be driven up. Stuff always tends to be more expensive in dense metropolitan areas. Big corpos and rich assholes would buy up as much real state as possible.
Traffic -> Without public transportation, this can actually get worse. The distances might be smaller, but the amount of people wanting to get there increases.
Homelessness -> directly related to cost of living. Having lots of places to live in that you simply cannot afford will force you to live elsewhere
I don't like the idea that the colonisers took the land at the barrel of a gun (inc in England with the Enclosure Acts) and we're demanding...a shell in return.
Well designed, small, community living based on the ideas of the Commons would be just as effective as all of the above without forcing us to live on top of each other having zero connection to the land effectively in dog kennels or shipping containers.
Anytime you have people living in dense, highly populated areas it will make nearby land a premium. High demand for land (and the resulting high prices) will result in high rent and high cost of living.
I'm not really sure how to fix this. You could have some government managed system for what businesses get the high demand land, but that will result in less popular stores being in the best locations and greatly incentivize corruption as businesses want highly profitable locations that can only be granted by politicians.