@NviGate Systems
There are scads of really old (as in pre-computer age old) machines and tools that will probably keep running and doing what they do for several additional lifetimes.
This is a band saw in my partner's wood shop:
And you want to talk about elevator technology that keeps on going, this is the freight elevator in his building that goes between the wood shop level and the level that abuts the train platform (the building dates from 1861, and was the flour warehouse for a milling complex):
112_S_New_Elevator.mp4
In 2014 I re-rigged the bullrope, which included weaving the ends together for the pull rope so it was a "circle" of rope. I had a professional do the work putting the metal eye and hook back on for the actual rope that carries the elevator at one end, and the counterweight at the other. In the video, I had not yet put all the boards back on that cover the counterweight channel, so it got stuck, briefly, when it was coming up past the edge of the floorboards. Here are the eye hook on the car, the counterweight, and the main pulley and brake:
As you said, there are many "early era of PC control" CNC machines that will very likely do the same provided the PC side of the equation is provided, and any business that has this kind of equipment, that's way more durable than what's made now and will likely live several additional human lifetimes, would be insane to replace it just because the PC side it needs no longer exists as a new off-the-shelf item.
It's a worthy cottage industry, including among techs, doing what needs doing to keep this equipment alive.