This is a famous paper by John Maynard Keynes. He saw that productivity was going to increase considerably over the next two generations, but really had no clue how that would play out. Now we're there, and it's not working out like anybody back then expected.
What Keynes missed was a consequence of a trend that could be seen back then - productivity increases are concentrated in certain areas, broadly, those involving "making stuff" - manufacturing and agriculture. In Keynes's day, that was most of the work force. In the US today, 14% of the work force makes all the stuff. (Yes, imports. If the US made all its own stuff, that number would still be well under 20%).
As a result, most of the work force is in low-productivity jobs - leisure and hospitality, retail trade, and health care are the biggest categories. Because each worker in those areas produces little revenue, wages tend to be low there. With most workers in low wage, low productivity areas, wages overall are driven lower. Although manufacturing could afford to pay higher wages, they don't have to be that much higher. A new hire in an auto plant today gets about half, in real dollars, what a new hire got in 1975.
That's part of how we got to where we are today. This wasn't forseen by prominent economists.
[1] https://www.marxists.org/reference/subject/economics/keynes/...