describing bitcoin this way makes it appears like ponzi scheme, as the investment of new commers are what is being used to pay the already existing customers on the platform, at the end of the day if they don't get new sign-up and people ready to fall victim of their scheme, you realize that the platform willl short down, where there are always people who pay for the rich of others, others get rich using the downfall of the next person, At the end of the day their is always a a winner and a losser.
But when it comes to bitcoin, We will always have those who are willing to buy and those who are willing to sell, and the value is determined by what the masses are willing to pay for it and based on its demand in the market.
Selling at any particular time is a choice; the same is also applicable to buying. If you decide to sell when the price is dumping and you happen to record some losses, that's on you, and the mistake that you made yourself shouldn't be shifted to others.
If we look at it this way, then we will feel that the whole world is based on a Ponzi scheme, every kind of trade in the world is done so that the buying party can take benefit from the trade when they sell later, and when the buyer is doing the trade, the seller is apparently already making the profit they once expected, that is how the world is running, we give benefit to someone and then get our benefit from someone else, but that is not exactly how a Ponzi scheme works.
In a Ponzi scheme, a single person or an entity takes money from both parties, and then that entity pays the one who has come first with what they get from the second person that the first person has brought to them, and that chain continues until the third-person who is receiving and processing the payments decides to run away with the money.