And... that's right, rol. There is only so much they can use up. Andrea taps that, too, just now. It's a major part of why increasing production efficiency hasn't resulted in an increasing workforce.
To supplement some of what 's said above, some of y'all seem to be forgetting demand and market saturation. You can't just infinitely ramp up your production and expect things to turn out well -- if no one's buying, or no one's willing to buy for more than it costs you to make, pumping out more stuff does sod all except lose you money and the ability to support what workers you did. If it's reached the point where the market just doesn't need the gubbin(s) your factory is tooled to build, or doesn't need nearly as much of it, or has stopping growing as quickly and no longer can support you increasing production as quickly, again, pumping out more does sod all.
Sometimes retooling is an option but there's a whole host of new variables that brings in, and it all it does is kick the can down the road a bit. The human population and especially those with the resources to buy stuff by and large hasn't been growing faster than our improvement in making crap -- that's one (of the myriad) reason(s) manufacturing et al caps, just hard, flat caps at a point and stops being able to keep up with increases in potential new workers. It certainly wouldn't keep up if we had been increasing workforce and subsequent output hand in hand with production.
It's, like. Materially, workforce, etc., etc. We could ramp up vehicle production, just as an example. We could ramp up vehicle production so much we would have literal mountains of vehicles (well, more of them, anyway) with no one to sell to and nothing to do with them, sitting there rotting, and then what? Broken window theory and the resulting mess of rusting steel only does so much, and there's other issues to consider as well (limited resources, mostly).
Or to point to something RP said, they were wrong when they flipped it. Flat Production Amount that we need a certain number of people to support is exactly what's going on, because more production past a certain point is less than useless.
... all that said, productivity gains isn't what's been causing QoL life loss in the areas manufacturing et al changes are hitting the hardest. Not adapting to it is what's causing that. Not retraining, not moving, not using the existent infrastructure (what there is) and expertise to dig out new markets, not having prepared for what was coming before the work started leaving. Far from all of that is even remotely the workers' fault (again, note everything I've mentioned previously re: funding, and add on to that the next to zero incentive businesses that more or less own towns have to future proof them), but... the QoL drop could have been avoided, or at least significantly mitigated. "All" it would have taken was everyone that had been working to reduce the funding and resources aimed at fixing the problem dropping dead, or at least out of politics, about fifty or sixty years ago.
But we haven't reached those limits yet, or we don't need to have. My point is that capitalist economics is, at it's core, about continuous trade of value between individuals which serves to produce, increase, or maximize the value of the goods or services being traded. If the generalized 'you' of manufacturers and their equivalents across different industries re-invest in their workers so that they have money to buy shit with, that creates the market which enables them to continue growing. The health of an economy is not measured by size but by motion; the higher the proportion of value that is transferring, and the more individuals it's able to transfer between, the healthier the market. When currency/value collects and goes unspent/untransferred, it's like a clot, except instead of being a sudden heart attack, it's a slow decline in health. So maybe more similar to toxins collecting in your liver or kidneys. Other than bubbles, at least.
More production of any one specific good past a specific point is useless, but production as a whole is not, as long as the economy is healthy. If the market of primary necessities is saturated, the market for secondary necessities remains open. If the market for secondary necessities is saturated, the market for supplementals remains open. If the market for supplementals is saturated, the market for luxuries remains open. The market for luxuries always remains open, so long as you are reinvesting in your market base to make sure they're healthy. It's like soil; you can just try to extract every bit of nutritional value and then move on, but you can only manage that for so long until it's all wasteland and you can't farm anymore.
...That said, manufacturing is not the only means of production, so I guess we're basically saying the same thing? I'm just saying that the markets don't need to be saturated anyway. And unless sale prices are already equal to cost-of-production+distribution, then there can still be more production without oversaturation.
EDIT: also it's super confusing when someone refers to Rolan and I in the same post since I'm not sure who they're referring to when they say 'rol'. In fact I'm still uncertain now since I'm not seeing Rolan's comment in the recent stuff
An extreme either way tends to be bad, so when you have one extreme threatening, you tend to be grateful for the other.