Bitcoin is a lot of different things to a lot of different people. The fact that it satisfies a certain set of conditions of a Ponzi scheme does not invalidate the myriad current and future applications of crypto. The social security administration could also be considered a Ponzi scheme, but it still provides tremendous value to a lot of people.
The Social Security Administration is entirely solvent by itself. The only "ponzi scheme" comes from congress using it like a piggy bank. And despite all that, SSA is backed by the US government. Bitcoin is backed by... nothing. So it's basically the equivalent of the zimbabwe dollar, not SSA.