I think the misunderstanding here is: What does productivity mean?
I interpreted the OP to mean productivity as "capitalist productivity" - meaning, how much money can you make for your king boss. People can still be productive in lots of ways that aren't considered "capitalist productivity" - for example, I love to garden, take care of greenscapes, and grow food on a small scale. Some people might not be able to do that, but they are wise and great at navigating social situations, and act as the center of their community. Both of those are productive, but often are not "capitalist productive", if that makes any sense.
So I agree with both OP and you - a person's value isn't determined by their ability to produce capital.