Let me tell you why you're wrong. The whole point of Ponzi scheme is to gain something out of nothing, in case of BTC and other cryptos who gains? Nobody.
Frankly, this is not an argument too.
1. If you don't personally see
cui prodest - it doesn't mean
nemo prodest.
2. A Ponzi scheme actually is to generate "profit" for oldies out of "investments" of newbies - this is exactly how bitcoin generates its "value".
And the last, but not least, you say BTC has nothing behind its price, but what about the energy consumption while mining, and the more there are Bitcoins - the harder it is to mine them
"Consumption" does not anyhow lead to "production" - mostly it designates the very inverse process.
Bitcoin "mining" does not produce anything but just digits that one considered to be
very nice. Someone else may consider as
very nice something else, for instance his birthday or digit string containing as many 8's as possible.
But don't worry: most of the stocks nowdays are more then a half a Ponzi scheme - as soon as their investors mostly count on the price growth, not the dividends