In a fraudulent investment scheme, like Ponzi, investors transfer their utilizable resources, be it money, goods or services, and then they end up with something which has zero utilization capacity, like promise or non-binding record of investment. After the investment, the only possible way for them to get utilizable resources back is if new investors join the scheme and in that way bring such resources with them.
BTC doesn't require new investors to maintain the illusion of value. It also does not have "zero utilization capacity." It does not have those Ponzi attributes. It may completely collapse at some point and/or all other crypto may tank or the tech transfer into something completely new, however that does not make it a Ponzi scheme.