"technology accretes even if the quality of the average worker is declining across time."

I cannot fathom how you possibly write this - surely you cannot be claiming that dumber and dumber workers develop better and better technology, or technology is some independent quantity that develops without human intervention, like a divine gift of some sort?

"a lower skilled person in a later period can still outproduce a higher skilled person in a previous period."

The last bloke operating the machine doesn't produce anything on his own, you have to compare the whole value chain, including the folks making the leather, making the tools and machines, etc. I am sure the old process includes plenty of people doing unskilled groundwork, although I would not bet my house on which way the dice would fall