Earlier quoted context omitted.
They thought that too in the industrial revolution. You can look back and see the jobs that came out of it. But at the time, it wasn't obvious to the people effected that there would be jobs again. We may have hindsight bias in evaluating something that happened, but to the people that it happened to it was terrifying.
MIT's motto is mens et manus : mind and hand. These are, basically, the two primary attributes of human labor. They're the reason almost anyone gets hired to do anything. Our brains and our opposable thumbs are what set us ahead of the animal kingdom. The industrial revolution first attempted to replace our hands. But the labor that was displaced had places to go: into smaller-scale manual work, where mass-production…
Nobody had any idea what was coming with the industrial revolution. There wasn't obviously other work for people. And for long periods of time nobody had an answer to that question for large percentage of the population.
In hindsight, we know the answers NOW, but then they did not know what was going to happen. We also don't know what's going to happen, it could go as you hypothesize. Or the Jevon's paradox people might be right and there's way more work to do.
The uncertainty is the historical lesson, not that "it'll all work out"