The low hanging fruit has been taken. Muscle power accounts for very little of the work people do. The making of physical things takes ever less of our total work, and the delivery of services ever more.
I'm not pessimistic in terms of what productivity improvements are possible in the future. But to a large extent they probably won't be as easy to come by. And the expansion of the effective borders of the economy to mean that it really no longer has borders is a big negative for the productivity of the leading nations. As many of the jobs that could have rising productivity instead don't, because they have falling wages instead.
I'm not pessimistic in terms of what productivity improvements are possible in the future. But to a large extent they probably won't be as easy to come by. And the expansion of the effective borders of the economy to mean that it really no longer has borders is a big negative for the productivity of the leading nations. As many of the jobs that could have rising productivity instead don't, because they have falling wages instead.