It's not productivity itself; it's the decoupling of productivity from wages. If I'm creating 3 times as much value as my equivalent in 1970, why aren't I getting paid 3 times as much inflation-adjusted money, hmm? It's not even unfair to shareholders - they'd also get 3 times as much as in 1970. But instead they get 10 times as much and I get 0.7 times as much, or something like that. What's the deal?
Ok, but that’s not what the post I replied to was saying.
> If I'm creating 3 times as much value as my equivalent in 1970, why aren't I getting paid 3 times as much inflation-adjusted money, hmm?
Because that increase in productivity comes almost entirely from technology owned by your employer.
To look at it in a contrived example, let's take textiles. There is a textile factory employing weavers who weave fabric by hand, and the factory owners buys a new automated weaving machine that makes the weavers each 3 times more productive. The maker of the machine created the technology, and is paid for it, the owner of the factory made the investment to bring the technology, and profits from it.
This is basically exactly what has happened to modern productivity.