Engineering plant/machinery is often decribed as “turn key”… having reached that holy grail point of "just turn it on! ".
I don’t remember any word specific to removing actual steps of manufacturing,
but terms like optimising, efficiency, engineering… re-engineered… updated… advanced processing technique would fit… nothing so specific … reduced complexity is there, but it doesn’t seem to be sensible, why would it be more complicated before ? it would have to be a change in process… or shifting the complexity to the controller… (computer software ?).
Saving on labour can reduce “total cost of ownership” or “operating costs”… because capital can last a long time while labor is paid for each hour.
NASCAR race teams hire highly trained engineers with this type of background to lead and run their pit crews because shaving seconds off in the pit can be the difference between winning races and championships and not.
I always think of “turn-key” as meaning more like “No customization required. Will fit perfectly into your existing environment with no adaptors needed.”
In other words, it speaks much more to the ease of initial installation and integration rather than to ease of daily operation.
My experience is much more in the software world than in physical manufacturing plant equipment. So your experience my be different.
In the selling of industrial equipment, one often encounters engineering firms or integrators that offer “turn-key solutions” which often means whatever it is, conveyor system, bottling machine, etc. they won’t just design it, they will build it and install it and have it up and running before they leave. It can also mean, as LSLGuy says, that whatever it is, it will work for you right out of the box (as it were).
This apparently first appeared in the 1920’s or early 1930s as “simplicate and add lightness” (or “simplicate and add more lightness”). It’s often attributed to William Stout (auto and aircraft designer), though it may have originated with one of his employees.