Enough with the straw man. The article's thesis absolutely does not hang on this interpretation, which only appears deep into the summary. Briefly, in contrast with a Ponzi scheme promising unsustainable returns on investment:

-There are no promises of huge returns

-The inner workings of the program are public knowledge

-There is no fundamental demographic or mathematical reason the system (a pretty straight-ahead social insurance program involving a certain amount of wealth transfer) should ever become insolvent, assuming the political will exists to keep it running.