While I have not seen the factories about which I fully accept you are totally qualified to speak, I have seen conditions here in the past which closely resemble those about which you spoke. Men (back then always men) driving crawler dozer devices over slag which had recently been tapped from a furnace. When you broke the surface it still glowed red hot as the blade pushed the 'rather warm' stuff about before it set solid. Or other locations where the machines proudly showed they had been built when Queen Victoria was still alive, hopefully you can imagine the rest of the conditions of the crumbling factories. Or see film of shipyard workers from when we built riveted ships, (there is a marker there to date when that was). Or casting iron products and knocking them out of the sand moulds before de-flashing them with a hammer and chisel or an angle grinder. Conditions were if anything worse and certainly no better.
What has changed is we no longer do such things we let someone else do the work and take the risks.
Your plastic parts maker is frankly ripe for a bit of automation, someone wrote of high earners designing goods in pleasant surroundings, fine. They should also design the production machine programs that will produce the damned things and let others do what we are still as a country trying to do, work in 'service industries', nice clean pressure free locations. Unless it is for example a fast food kitchen where the pressure is relentless, the temperature is high and the pay is still lousy. There are still loads of crap jobs going at minimum rate, which frankly need automating if we can train enough people to build and service the robots to run them.
It was going to be 'the end of the world' when hand looms and hand spinning was automated. Now we have more workers than ever so don't try the old 'automation kills jobs' trick. Dumbly exporting work kills jobs that is true.
I'll will make it simple, really poor management, poor pay and unskilled workers kills jobs faster than anything else.
It will come to those who wait to be harvested.