Ok, so hold all your assets in real estate, stocks, or gold and only convert it to fiat when you need to pay for something. I'm not sure what cryptocurrency adds here besides another (rather volatile) investment vehicle.
bit late, but: real estate and stocks (and most gold) isn't held sovereignly, but in vaults, managed by gatekeepers. I own some stocks though a platform that manages it for me. They can force me off their system at a moments notice. Real estate is managed by the government. They can also take it away.
The first counter-argument would be that we have laws and procedures that protect most people from such actions, which is mostly true. There are however a number of clear examples where either the government or society underwent rapid change which allowed for these assets to be seized (think: revolutions, exectutive order 6102, etc).
Bitcoin (not crypto -> bitcoin) solves this through offering you the option or sovereignly hold an asset outside the control of anyone who doesn't have the private keys.
Sure, the monetary system is flawed (in the sense that all systems are flawed and the current one seems to be doing particularly poorly _at the moment_) but we also had a trustless central banking system before called the Gold Standard and iirc that didn't work either? What is it about digital currencies that make this better than the Gold Standard?
Bitcoin isn't a solution to trustless banking. Its a solution to trustless _central_ banking.