You seem to be confused about the point people are making. The point is that from about 1945 until around 2000 in the USA there really wasn't such a thing as "a job that doesn't pay enough to live on".
People owned houses and cars by working at grocery stores. A single income from any white collar job supported a stay-at-home spouse. Teenagers bought cars by working part time. College kids paid their tuition and living expenses for the full year by working summers.
That today's below-poverty-line job still leaves someone better off than being completely destitute is beside the point.
You're just cherry-picking though. Things were massively different in 1945 in tons of ways. For example Jim Crow was still active for one. Food prices were MASSIVELY higher for another.
I understand that argument, but what does it have to do with the unemployment rate?
You seem to be confused about the point I'm making, which is that low-paying jobs drive people to take on more employment, not less.