Technically, Jerome Powell did. Currency valuation is complex because it is relative so the lens of perspective becomes everything. The primary nuance in your example is that currency devaluation through inflation is not the same as currency devaluation through a decrease of adoption (and therefore overall buying power): this is very clearly reinforced by the IMF's criteria for what a currency requires to become the global reserve. Any modicum of "objective" value can only be reached through multiple relative comparisons. For example:

- How many Dollars does a bitcoin buy?

- How many Bitcoins does a Dollar buy?

- When the exchange rate varies, what does that say about the relative value of each currency?

- How many Potatoes can a Dollar buy?

- How many Potatoes can a Bitcoin buy?

- How many Drugs can a Dollar buy?

- How many Drugs can a Bitcoin buy?

The above is extremely oversimplified but much like a global foreign exchange relies on shifting exchange rates, so does the value of all currency in terms of relative buying power. In terms of absolute buying power - my personal highly subjective bid is that a currency's "value" is a compound of its' exchange rate as well as the amount of people willing to exchange it, and the amount of it in circulation as well as the breadth of people willing to accept it in exchange for goods and services.