Now there are all manner of divergences from the above paragraph. Coins that are totally controlled and issued by a small group or company. Black box rules rather than transparent.
There are also huge trade offs with not having a central entity - lose your private key and lose your money for example.
Does this make the entire industry a Ponzi? No. There are legitimate uses for crypto, and even if I listed a whole bunch here the HN skeptics would disagree, but certainly buying drugs online is a real use case, which crypto excels at. You may say that’s morally wrong but it is still a use case, for better or worse.