I think many people in these comments are bound to talk past each other when the real answer is:
Yes, Bitcoin is a Ponzi scheme (by virtue of people making it so), but that does not, nor should it, imply that the only thing Bitcoin is, is a Ponzi scheme.
Bitcoin is a Ponzi scheme in the same way that sociopaths exist in the game of geeks, mops, and sociopaths:
https://meaningness.com/geeks-mops-sociopaths
It's part of the ethos but does not describe the whole ethos, and trivializing Bitcoin to a Ponzi scheme is the wrong answer. As, honestly, is trying to defend that Bitcoin is not a Ponzi scheme.
Irrespective of how value is in practice (or volume) making its way through the system is different from the system itself.
There are several promising elements of Bitcoin which contribute to its value. One is sheer access and connectedness (e.g. Metcalfe's law). People use facebook (its valuation reflects this) or pay for a phone plan because connecting to the Internet is a synecdoche for ubiquitous access. Creating a fabric where people in any country may work for a company, irrespective of its location, is a paradigm shift from what we had previously. Today, working for a US company from Taiwan is a legitimate challenge & deterrent.
There are many such examples, where transparent ledgers for instance may increase trust between parties and give people more confidence in financial robustness. All of these things have intrinsic value, just as the architecture which is PageRank has value for Google.
A common mistake I hear is for people to point to these advantages as if to suggest that it is without flaws or incapable of flaws, when we -- the people using the system -- are quite fallible and driven by prisoner's dilemma-type incentives which may by no means be long-term efficient or equitable (given we're all in the same boat). And I think these social challenges should be noted and not discounted on behalf of "technology being good enough".
So, I think this is a case of "Yes and".