It's funny you can say that about pretty much anything. If it's not cash on yourself it's not your money, or all sort of other assets where ownership is essentially backed by the government. The issue with all these crypto schemes is, people want to get rid of government oversight when it's inconvenient for them (e.g. have to pay taxes) but otherwise still want the government to guarantee ownership of actual physical assets, because it would be pretty inconvenient to loose the mansion you bought with all the crypto gains.

And this aphorism conflates ownership with possession. Crypto is a bad actors fantasy turned reality.

Non custodial ownership is still an option, even if not advisable.

If my non-tech savvy grandma wanted to own some bitcoin, I'd probably suggest she just keeps it on the exchange. Counterparty risk is probably less than risk of user error.