I didn't say it was incontestable. I only said that it seems to be the case and that the evidence seems to favor that opinion. It would be more interesting to hear why you think it is contestable. Also, I'm not sure how this is tautological.
> But also - consider that that humans have cognitive and physical limits.
If anything, that would seem to suggest that these impose a bound on how much we can automate. Arguably, this means an upper bound would be determined by the maintainability of such technologies.
> Even if there is in principle always new opportunity created by automation, which I do find plausible, I see no logic supporting the idea that these new opportunities would necessarily be widely addressable by the majority of humans.
If you are making that claim on the basis of cognitive limitations, then see my previous point. But by the same token, if cognitive limitations impose a limit, then it would seem to suggest that the problem space would require a greater division of labor in order to render it tractable.