We know the statement "More technology always means more better jobs for horses" is both silly in theory and demonstrably not true. Could you provide an argumen

We know the statement "More technology always means more better jobs for horses" is both silly in theory and demonstrably not true. Could you provide an argument for why it is true when we replace horses with humans? I'm aware that the economy as a whole will be better off, but if suddenly a quarter, a half or even 90% of the population becomes superfluous, it'll be debatable that society will be better off.