Part of the reason I think 21st century automation is different from 20th century mechanization is that when you mechanize jobs, that requires physical machines, and the number of factory workers and mechanics needed to build/maintain those machines scales linear-ish-ly with the number of machines needed. And so mechanized farming got rid of a lot of farming jobs, but also allowed more farms to be built, which required more and more machines, and thus created manufacturing/mechanic jobs.
Software jobs don’t scale like manufacturing jobs. If you automate a particular profession’s work, they’ll lose their jobs, but meanwhile maybe now 10x more customers can afford the service they provide. But now, scaling the automating software to serve 10x the customers won’t require 10x as many programmers, maybe just a couple good devops people to tend the flock.
You might then argue that customers will still find things to want from the newly freed up labor, but I also think we’re going to start being hard-pressed for categories of work where “the human touch” makes a difference, and also where there is room to employ large sectors of the workforce. Add in that customers “new demands” won’t necessarily correlate with the need for human workers, and it becomes easier to see a world where people keep coming up with new wants, and automation keeps swooping in and immediately satisfying the demand.