I'm not comparing it to farm work, but to what it could be.

You don't seem to realize that allowing labor to move from critical/essential work to nonessential work is a good thing. That's how the system is supposed to work. What would you call sommeliers, chefs who create Michelin-rated restaurants, movie stars/writers/producers, surfing instructors, etc if not nonessential?

Automation makes things cheaper. Look at food, it was the largest expense for most families for a very long time. Now for most families in the US it's not even close. We have taken the jobs that used to be in that area and gotten rid of them, and instead moved them into service industries like the ones I referenced above. Making things cheaper means more disposable income to be spent on luxury/nonessential items, which creates a market which didn't really exist, which in turn creates jobs. This is not hard stuff here.

Yes price reductions lead to new demand, hence new jobs.

But what if for almost every human supplied product/service there's a good enough machine substitue, or even just a human substitue that demands very little labor ? couldn't we reach a stable state of high unemployment ?

There are still a bunch of jobs where machines are unlikely to replace humans anytime soon or ever, because the cost of deploying machines everywhere and maintaining them will also reach a plateau. We may be good soon at making brains for machine but they still need mechanical parts and require maintenance. So they have a non negligible cost.

>You don't seem to realize that allowing labor to move from critical/essential work to nonessential work is a good thing. That's how the system is supposed to work. What would you call sommeliers, chefs who create Michelin-rated restaurants, movie stars/writers/producers, surfing instructors, etc if not nonessential?

I call them "creative professionals who do what they do by choice".

The majority of non essential work is not "movie stars and Michelin chefs", it's either automatable burger flipping or bureucratic busy-work created to overcome the lack of a system for distributing social wealth outside of "roll around for it".

To put it in another way, we could maintain our current production and give free massages and pedicures to everyone with far fewer jobs than we have now.