1) In agriculture at least it doesn't - many small competing producers can produce a lot more efficiently than one big one with no checks on inefficiency. There's a lot that's fucked up about Big Ag but most of the egregious stuff (like corn subsidies, or small sharecroppers being forbidden to own or save their own seeds because of IP restrictions) would be fixed by more competition and less government involvement.

2) The economy shifts into the next phase of development. I don't know what that'll be - artistic pursuits? space exploration? - but eventually the service industry will face the same fate as manufacturing and agriculture, and we'll move into a new economic era.

> artistic pursuits? space exploration?

Perhaps artistic pursuits in space :)

Humans don't take boredom well. They'll find something to do even after all their needs are fully met.

Art is a service. I’m more curious about what people would do to get any of the things that are currently “the economy” when all needs are oversupplied by, say, a mere 5% of the population in full time work. Would people work less for the same goods? Would there be high unemployment? How do things shift and rebalance? UBI sounds good, but is it politically feasible — some people get called “benefit scroungers” while others are called “pensioners” and “the royal family”?

Communism, mate, that's communism come true.

1) Soviets did this with a mixed success.

2) we'll do something else

1) Soviet example is not useful, because manufacturing wasn’t “minor” back then.

2) what “something” is neither primary production, nor manufacturing, nor services, yet capable of being scarce in a way that could be meaningfully traded for the aforementioned?

If you are talking about agriculture, well, it was a mix of bad and horrible that every other country that adopted communism worked very hard to find a different model.