If membership in the community of Bitcoin holders has "value" to someone he/she is free to investment his/her entire savings into it. But he/she won't be able to benefit until a new member enters the community. And this is exactly how all fraudulent schemes operate. And that's why they all eventually collapse.
Money is something that doesn't require the addition of a new member to be able to provide benefit to its holder. That is because the benefit comes from the entitlement or utility that is behind money.
If the purpose of Bitcoin was that buyers "benefit" from it
simply by hodling it, then it has ponzi-like characteristics.
But that isn't the case. Bitcoin was designed as "peer to peer cash". The ultimate goal of those that follow Satoshi's original principles is that BTC eventually should enter a stable state, where there is no need for "new members" to enter the system, because it's not used for speculation but for trading goods and services, with an independent money circulation taking place in the Bitcoin ecosystem. In this scenario, the Bitcoin price should stay relatively stable.
And here we come to the question of "utility". If we reach the situation where the Bitcoin price is stable, how can people benefit from entering the Bitcoin ecosystem? Simply because it may have characteristics that are superior of other kinds of money. For example, you can simply send money from one country to another. You can get basic privacy (not a perfect one, but better than most non-crypto competitors). You don't depend from single private entities, like with PayPal and friends. And many people do already use Bitcoin to remove their dependancy of the government issued currency of a badly managed country like Venezuela. In the future, we can add that eventually it
may become one of the most accepted forms of money. We don't know, but isn't impossible.

Ponzi-like characteristics do not reside in "holding" an instrument. You can "hold" stock or bond certificates (records) but that won't make them ponzi-like. Ponzi-like characteristics reside in the inability of a holder(scheme member) to benefit from his/her instrument unless the new member voluntarily chooses to buy it. Bitcoin holder can benefit from bitcoin only if someone voluntarily chooses to buy it. This is because no one is obligated to trade his/her goods or services for bitcoin. On the other hand, in the case of dollars for e.g., borrowers are obligated to repay their loans and thus obligated to trade their goods and services to dollar holders. If they default on these obligations and fail in such trades, the banks will foreclose their property that was pledged as collateral and sell it to dollar holders. This is because the created dollars are the liability of the banks, and they are as such recorded in their balance sheets. To put it differently, dollars are records (digital or paper) that grant their holders the entitlements. The same is true for bonds, or stocks - they grant their holders the entitlements. Bitcoin doesn't grant its holders the entitlements, which is why these holders can benefit only from the entitlements (dollars for e.g.) or need-satisfying goods that are brought by new members. And that's the definition of a ponzi-like scheme.