There are other productive activities besides those that increase your wealth. For example, if I'm trying to learn an instrument, then I would consider practicing to be a productive activity. In this sense productivity is not a scam at all; it's a necessity to live a good life.

Speaking purely in terms of money: yes, doubling the productivity of those working for you is better than doubling your own productivity. But many of us don't have that option. If you are a normal employee, increasing your productivity is one of the few ways to increase your earnings.