how it goes down is important though. if automation follows after labor begins to move to something else then that's one thing, but the reverse, automation putting people out of work, mean there might not be anything for them to realistically move to.

A booming business in automation and robot repair.

The whole point is that you need fewer humans in the loop. If every factory worker automated out of a job was hired back to work on the robots, we'd skip the automation part entirely.

Good luck learning to program or repair self-driving trucks when you've been a truck driver for your whole career.

Self-driving trucks have mechanical parts too. Even if you automate basic mechanical maintenance, operation and supervision will still require human intervention for a relatively long time.

One of the bigger issues now is you're competing with the entire world. When global shipping can get any product almost anywhere in a few days, economy of scale wins.

With oil becoming more expensive, for how long do you think global shipping will stay cheap? "Economy of scale" is many times an euphemism for "burn fossil fuels with subsidized costs".

We can go back to using sails. Cheaper but slower, so it'll work for a portion of shipping

Yes, and they where replaced with mainly useful jobs. But how many useful jobs can keep coming up with ? At what point does it just become sick extravagance of goods(materialism) and services we do not need?