Sometimes we need less. In fact, there is some advantage to single people living in very small spaces, since it encourages them to get out of the apartment. The limited space also discourage accumulation of lots of stuff. But you know what will come next. Activists will discover the “injustice” of the small space and demand a “livable” standard.
Fairfield Inn where I stay in South Hill has a kind of mini-suite with a bedroom separated by a half wall from a kind of sitting room. The King Suite, which is 375 sq Feet, would be sufficient for an individual or a couple w/o kids. They would have to be organized and frugal, i.e. not have too much stuff, but it could be pleasant enough. That would be a nice design for an apartment building.