Cookie cutter bland housing is considerably older than the mid 20th century, we don't see much in the way of old examples because this sort of housing is not meant to last, it is meant to meet a need. Most of the mid century stuff is considerably nicer than what came before, like the tenements of New York and various housing projects built around the country including large developments of single family homes with spartan interiors and all. We needed houses and we needed them fast, a single model with few frills was the only way to meet the need at that time.