It is an object of no intrinsic value, even to the extent that as an 'object' it doesn't even exist, brought into existence solely by decree ("I/we have created Bitcoin, and I/we hereby declare it to have value, or even the ability to have value as a medium of exchange"). Opting to attach that value to the currency of some other government (which currency is itself fiat) only pretends some separation exists between the crypto and the force used by that government to maintain its currency. Because you have someone else committing the violence by which you benefit doesn't mean you aren't perpetuating that use of force.

As for its voluntariness: everything is voluntary for the rich, and the rich are clearly who dominate the ownership of the vast majority of crypto. Which only further sinks the whole 'decentralized' idea. How can it be decentralized when the vast majority crypto is owned by such scant few?