The mechanization and scaling up of farming caused a tectonic shift from rural residents moving to cities to take on factory jobs as well as office and retail jobs. We saw this in China until very recently, since they had a bit of a slow start causing delayed full-scale industrialisation.

So a lot of people will end up doing something different. Some of it will be menial and be shit, and some of it will be high level. New hierarchies and industries will form. Hard to predict the details, but history gives us good parallels.