Yeah and anybody who loses their money on the stock exchange, already spent that money on a security and then the security lost value. What's the difference?

The GP seems to be implying that using bitcoin is risky, which is true, but as evidence cites someone who lost money while not holding bitcoin. I'm sure people also lost CAD they had been storing in Quadriga; when you put money into an uninsured bank/exchange you might lose it, losing it is not evidence that bitcoin itself is risky.

You can’t spend Bitcoin anywhere which means you need to rely on these exchanges to get something you can exchange for goods and services. This makes them a mandatory part of the exchange transaction and ecosystem as such their risk must be factored in. You can’t pretend the platonic ideal exists for crypto when comparing it to real world pricing and risk for existing solutions. That’s disingenuous at best.

With bitcoin the choices seems equivalent to unsecured banks (trust someone else), or gold bars under the mattress (hope they don't get stolen, you don't get incapacitated and they get forgotten about, etc). I wouldn't want to store a significant chunk of my savings in either of those situations.

current state of the art is not very good, storing large amounts of cryptocurrencies is not as convenient as large amounts of fiat and it may never be as convenient, but usability is slowly improving.

Hardware wallets and safe deposit boxes and multisig let you build a system which is far better than storing your money in an unsecured bank and far less vulnerable to theft/loss than the mattress strategy.