Civilization is a ponzi scheme if you step back far enough, but it's not a useful way to model it. For a more accurate understanding of the way Social Security is structured, I would check these links. The second link is to an interview where it's explained in simple english.

https://www.ssa.gov/policy/docs/chartbooks/fast_facts/2019/f...

https://us14.campaign-archive.com/?u=bd0d1b66f832083794c33c9...

I also have not found a source to substantiate the claim that the US government periodically steals money from Social Security.