But that's true for all ponzi-like schems - they are all backed by nothing and - their value is determined by the people who uses them.
You CAN'T have something decentralized but at the same time backed by something. It's an oxymoron. Goddamn it's already 2020 and we're still not done with the ponzi scheme argument.
Selling them is how this scheme operates in the first place. All ponzi-like scheme operate by selling their membership stakes to the new investors. So, the question is how can you benefit from bitcois without selling them to a new investor?
You don't even need to sell it 100% of the time. If you want to use bitcoin without selling it, then transact with someone willing to receive bitcoin. Also, what's really wrong with selling bitcoin? If we're doing a transaction for instance, and I prefer receiving EUR instead of your USD, you could simply convert your USD to EUR to comply with my terms. The conversion from USD to EUR is pretty much the same with the conversion from BTC to USD.
Receiving bitcoin for the sake of receiving it is also what I can do with someone's Excel record. The conversion of currencies is buying and selling them. I will repeat: the whole point of this topic is the question how can you benefit from bitcoins without selling them to someone.