All I can say is thanks, but yes, every thread of this variety gets a bit tiresome hearing the same things over and over that tend to be some variation of "my peeve local issue with the US is the reason the US experiences a problem experienced by hundreds of other countries with wildly different policies."
Not to say, in a vacuum, multi-family housing won't provide more housing units per unit of land area than single-family. Clearly, it will. But unless you build every city from scratch to house 20 million people, whether you started with single-family or multi-family, the most desirable cities will end up in a future state whereby more people want to live there than housing exists for, and even if regulations and zoning allow you to build higher and denser than is currently done, to do it where people want to live, you'll have to tear down existing buildings, including existing housing, and many of the owners and occupants of that housing won't want that. You'll also need to run more utility lines, build new pipes, run them under existing roads, which means shutting down those roads, and even if they're perfect utopian European roads that have zero cars on them and only have pedestrians and bicycles, the user of those roads are still going to get annoyed and inconvenienced, and it's going to cost more to do this than building new housing where nobody currently lives, pretty much no matter what.
Not to say, in a vacuum, multi-family housing won't provide more housing units per unit of land area than single-family. Clearly, it will. But unless you build every city from scratch to house 20 million people, whether you started with single-family or multi-family, the most desirable cities will end up in a future state whereby more people want to live there than housing exists for, and even if regulations and zoning allow you to build higher and denser than is currently done, to do it where people want to live, you'll have to tear down existing buildings, including existing housing, and many of the owners and occupants of that housing won't want that. You'll also need to run more utility lines, build new pipes, run them under existing roads, which means shutting down those roads, and even if they're perfect utopian European roads that have zero cars on them and only have pedestrians and bicycles, the user of those roads are still going to get annoyed and inconvenienced, and it's going to cost more to do this than building new housing where nobody currently lives, pretty much no matter what.