Compare the working conditions of those jobs to those of current white-collar work.
You could reframe as underemployment a lot of the extent to which jobs in the past were less stressful (if they actually were). Trading stress for fantastic material wealth is a highly popular option afforded by technology.
The numbers say you're wrong: http://www.nber.org/aginghealth/summer04/w10466.html
You show me a graph that ends two decades ago. About poverty.
The current poverty rate for seniors is now below that of when the above graph cuts off, naturally [pdf warning]: https://www.census.gov/content/dam/Census/library/publicatio...
Of course it is still valid to ask how a healthier workplace could be created. Just the notion that things were better in the past seems very unlikely to me.
America seems to be trending towards the Asian model of work.
I honestly had managers at the Kmart retail store I worked at who struck me as smarter (and certainly more humble) than at least one software manager I've had
20 years ago, before the lax in regulations made the whole world a competitive nightmare for most workers.