Gaming

They aren't saying crypto is a ponzi scheme, they're saying play to earn is a ponzi scheme. Saying pay to earn isn't a ponzi scheme because more money is minted is like saying a ponzi scheme isn't a ponzi scheme because the fed prints more money. Ponzi schemes are a business model where the majority of revenue comes from sign-up fees and investments, the economy they exist within is irrelevant.

That being said a lot of cryptobros seem to want to use crypto as a ponzi scheme so it's easy to see where people get that impression. Pump and dump can be framed as one - the initial investment is people buying the crypto or dedicating resources to mining it giving the illusion of increasing value, then the people with the most crypto (top of the pyramid) "dump", causing the model to collapse and extracting surplus value from people's investment. This isn't inherent to crypto more than any financial system though, it's a side effect of the economy being small enough that individual actors can cause a total market collapse and people treating it as an investment rather than a currency (possibly promoted by crypto being deflationary?)