That's actually exactly why it took the Romans so long to technologically advance. "The slaves do the job well enough".
The idea of water powered mills and general aqueducts were mind-blowing to them and took a while to catch on. It seemed utterly unfathomable when everyone relied so much on slaves
Which is similar to my theory of why the industrial revolution took place in the west. High populations in the east meant that labor was always cheaper and more efficient than trying to get compliacted machinery to do the job. It's why a lot of manufacturing still happens in the east, because machines can't do everything and the best robot is still a human being with a good jig.
And within the West it was in the places without slavery. As countries gave up their colonial slaves, serfs, peasants, etc. they started advancing. The countries that reverted back via fascism and the like saw themselves broken.
A slave works to the point where they are no longer whipped. An employee, in theory at least, is rewarded with higher pay for being more productive. Sometimes I wonder if anyone has researched the industries that pretty much pay everyone the same minimum wage and their output over time. I go to client sites and some of them everyone is paid terribly and the efficiency is staggering low.