With ETH for example, I can create a new EIP, and if the majority of users agree with it, the currency can evolve. For example see EIP-1559 adoption despite it going against miners best interests, or even EIP-721 which has led to profound changes in the way the network is now used. This is pretty much "majority rule" but obviously it is being driven primarily by developers and those with the technical knowledge needed to propose and shape these EIPs.
On the other hand, with USD (or any state currency) I have nearly zero chance of influencing its policy, inflation, and so on. The only option I have is to write to politicians and hope they take it further. If the politicians (governing body) in place do not currently agree with this policy despite a large (user) backlash, there is no way for users to "fork" the USD, and so they are forced to adopt whichever decisions are made by their current government and policy makers. This is especially true if you live outside the US (as I do), but are still required to use USD by virtue of working with US clients, US customers, and primarily USD-based payment systems (e.g. as Wikimedia is stepping closer toward with this change).
This is mostly just presented as a thought experiment in response to the idea that USD is far more democratic than an open source + decentralized currency.