Historically, more efficient agriculture meant a population boom. That's kinda the opposite of people starving to death. A lot of agriculture historically and in poor countries like India today is subsistence agriculture, yeoman farmers living off what they grow directly. More efficiency allows them to sell their surplus and to invest the proceedings, kicking off economic growth.

Or we take some small portion of that new surplus in productivity and share it among everyone by divorcing the need to work from the need to not starve.

>The flipside is that there must be other work to be done or people starve to death

false. people are not helpless and jobs are not fixed in number nor social welfare gifts. Human creativity and industriousness can be put to task to produce things that other people want. In an absurd example, you could live next door to a new efficient sweater mill, and you could still knit handmade sweaters, customized with people's initials, etc., and their sale would measure the value of your output in. dollars. People don't do this very often because such an economy produces more lucrative jobs than that.

doomers have foreseen the end of the world in every generation going back. The bad speculations have never come true, but there have been some very negative outcomes of fearful people believing the doom and gloom, look no further than the seeds of Marxist revolutions, Fascism, and Naziism, they all start with people feeling economic uncertainty.