"Technological improvement actually did lead to widespread unemployment once: the Great Depression."
Economists argue about the causes of the Great Depression, but the idea that the Great Depression was caused by improvements in technology is not one I've ever heard.
If I recall correctly, Einstein himself said it. (I know, wrong area of expertise. But he is famous.) And now, productivity (as measured by the GDP per employee —I know it's a flawed measure) literally shot through the roof since the 1970s.
When production rises for whatever reason, either demand rises with it or we eventually have unemployment. I understand you never heard the argument, but why would production rise? I only see two reason: population growth (no problem, demand will rise as well), and technological advancement.
Now, technology also increase demand. We all want more modern gadgets and all. But it is not clear this growth in demand outpaces the growth in production.
Economists argue about the causes of the Great Depression, but the idea that the Great Depression was caused by improvements in technology is not one I've ever heard.