Ponzi and Pyramid Schemes: Cryptocurrencies

I have seen the words "Ponzi" and "Pyramid" being dropped quite a lot in multiple threads, usually in regards to Luna, Celsius, etc.

On the conventional stock market, a Ponzi is usually referred to a broker that promises high APY%, fails to responsibly manage investors' money, or deliberately does not manage the money, while the investors do not hold an accurate visibility of the brokerage's real value. So essentially, the high returns that are given to trader X, are partially or fully based from from the money invested by trader Y. And when the time comes and more traders try to take profit or cash-out, the company starts crashing due to insolvency. One of the more famous examples to that was Bernard L. Madoff's "Investment Securities".

But what makes a cryptocurrency by itself a Ponzi scheme, or a pyramid scheme?

Some Redditors argue that it is:

- A product (coin) with no real market usage, other than for pure speculative investment purposes. So if that's what defines a Ponzi, does that mean that every cryptocurrency other than BTC, ETH and XRP, and perhaps a handful more, are all Ponzis by definition?

- Cryptocurrency sold with no actual value backup. So you mint as many coins as you'd like, or you cap them to a finite amount, but the producer does not have any alternative underlying value to back-up the worth of these coins, as they rise in price.

What do you think?