That theory was based on the idea there was a fixed amount of wealth in the world and it was impossible to create more.
In fact it rather sounds like an intentionally foolish theory invented by someone practicing usury as the only possible reason anyone could disagree with them, and then incorrectly attributed to any opposition to their practice. You can sort of tell this is the case, because if you reverse the theory you get “usury creates wealth while other activities just shuffle it around”, which is a very flattering thing for an usurer to believe.
Unfortunately today usury is so endemic that people can't see any other way of living, even though debt-free publically issued money is an obvious possible solution to many issues we face today. See social credit (canadian, not chinese)