Hmm. I kind of guess that the mid or late 20th century hit a sort of 'sweet spot', kind of likened to an intersection between the 'supply' and 'demand' curves on a graph.

Currently the world population is 7.9 billion. From 1960 to 1975 it was between 3 and 4 billion. The time in history also allowed for a greater diversity of jobs (agricultural, industrial, and beginning tech) and HUMAN labor was still important.

But, currently, automation has made a lot of low-skilled labor obsolete. So, there is less of demand for HUMANs in many job sectors (agriculture and service). But, there are so many more people on the Earth.

So, it's just not sustainable anymore, I think. I used the Victorian Era as an example because our expectations naturally change over time. What I'm saying is: most Victorians didn't expect to live independently on a single income. Maybe we should change our expectations. Maybe it just isn't possible anymore, unfortunately.