That assumes there is a fixed amount of stuff todo/needed.
Sometimes making something cheaper to make, just means you make more with the same people as demand is elastic and price driven.
The other question is if you need less people ( less say for farming ) is there anything else these people can do ( ie work in factories ) - that depends on whether there is fundamentally enough tasks to go around.
If you look globally it's quite clear that even the basics - like clean water, enough food and decent housing hasn't been sorted. ie there is plenty of work still to do done.
