This is a good question - I haven't studied much aside from densifying existing neighborhoods but when thinking about other options, I suppose suburbs come to mind. Before going any further, I should clarify that I live in the US and look at this through an American lens. Anyways, a primary issue with suburban affordability is that demand is high and space is limited[1]: many folks want to live in the suburbs but maintain their jobs in urban centers, and you can only have so much low density housing within commuting distance to a city. Since urban centers are where the majority of jobs are, it's tough to suggest that people "just move to the country", for example. Remote work could help with reducing density while allowing people to relocate to more remote and/or affordable places. More public transportation may also allow suburbanites to move further away (think high-speed trains and commuter rails).
I've also heard arguments for an urban model that focuses on smaller, more community-centric cities instead of huge urban centers like New York or LA. I don't have any primary sources for this, but I think the idea is to keep density low-ish, and increase the distribution of these urban nodes evenly across a region [https://en.wikipedia.org/wiki/Urban_village]. To me this sounds similar to the mundane suburban towns I grew up around.
Urbanity/density is likely the easiest[2] solution, but I'm sure it's not the only one. There are likely many thoughtful solutions that don't rely on density - I may look around to see if I can find any.
[1] I guess this issue applies across the entire spectrum of housing, which is why there's a housing crisis
[2] Easy is relative - obviously, this is has proven to be a very difficult problem to solve.
LA is close to the logical end of the model you describe; downtown LA is a fairly weak center and there are other nodes as well.
In practice this just means that instead of commuting in long distances in one direction, you do it in every direction. People just tend not to live that close to work due to different desirability characteristics for jobs vs homes. And for multiple income households this is even more difficult, because how often do all the people in a single house work or go to school in the same neighborhood?
i get the impression dense urban environments are ripe for various types of capture not to mention the variety of competing interests that end up diluting the effectiveness of policy to address these issues.
also, i get the impression incentives for housing developers aren't aligned to addressing this problem because in the end it would mean lower margins and a smaller pipeline of future housing development projects effectively putting them out of business.
Keep in mind that, if the barriers of entry are low enough, property development is nothing like a cartel.
Developers will happily undercut each other to steal their competitors’ lunch.
The current model actually promotes cartel behavior; there is so little developable land that it is possible for a few people to hoard the small supply of land.
