Is this really true? Unless urban renewal demolished them wholesale, all late 19th century neighborhoods exist virtually fully intact. There was no filtering of low quality vs high quality.

Beyond that, in the area I refer to, Southern New England, the vast majority of those buildings are still in everyday regular use, and with the exception of obsolete institutional or industrial buildings, very few have been demolished. Of course, some got leveled to build bigger buildings, but not that many. I would say 95% of residential buildings within a mile of me are from 1915 or earlier, most of them timber framed, and my neighborhood has about 15k people per square mile, so it's a decent sample size.