We can build to modern standards fine. The problem is usually you're not allowed to build at all. Nearly every jurisdiction in the west has tight supply caused

We can build to modern standards fine. The problem is usually you're not allowed to build at all. Nearly every jurisdiction in the west has tight supply caused by nothing except laws and zoning; there's nothing about the air or the dirt preventing a bigger building. I don't think people necessarily want to go back to the 1900s and share a ten square meter apartment with a 3-generation family, and then die in a fire because that's too many people to evacuate out of one door.