> That's a false dichotomy, because those people can go and do something else.

That is not automatically guaranteed.

Part of the problem with the Western economies is that the mills/mines/etc. used to employ a LOT of people.

A good example is the Natrona Heights steel plant. It used to employ something like 10,000 people at its height. After automation, it will now employ a couple hundred.

Where do 9,500 people switch employment to?

This is why we need to get past the idea that everyone needs to work to earn a living. Why does anyone need to earn the right to live? Our society has enough empty homes to house the homeless, and throws away enough food to feed the hungry. Why are people still homeless and hungry then?

Take your example of the steel plant. Presumably when the 9500 people were laid off, productivity remained the same (or increased) and costs went down. Where did the extra profit go? Was it dispersed among the remaining 500 workers? Was it used to help the displaced workers who devoted years building the steel mill and keeping it running? The very people who designed, forged, and brought on-line the machines which replaced them? No, the upside went to the owners, because they have a slip of paper that says they own the mill.

Our problem is not that we're automating away jobs, it's that the displaced workers don't get to share in the benefits of that automation. Eliminating a job is seen as a disaster, rather than a victory. We should want to eliminate terrible jobs, not keep them around just so someone can stay busy. And I guarantee you, people who don't have to work will find something to do. There's always work to be done, just not all of it is profitable (e.g. raising children, taking care of the elderly, volunteering, open source coding, etc.)

There wasn't extra profit because all the mills automated and they are all competing with each other. If expenses were lower, one would cut prices to gain a market advantage, others would follow until the price reached its floor.

There were plenty of profits to be had. I've lived in steel towns almost my entire adult life, and you can see exactly how that manifested in region. Drive around these towns and you'll see the names of wealthy steel tycoons on roads, parks, schools, and even whole towns. You'll also see stark divides between streets with lavish mansions where management lived, and dilapidated row homes where workers lived. The divide was so deep that workers literally fought and died for better conditions at a time when steel prices and profits were actually increasing (https://en.wikipedia.org/wiki/Homestead_strike).

Ever heard of Carnegie Tech (CMU), the Wharton School, or Swarthmore college? They exist precisely because of the existence of massive profits from steel.