This is over simplified. Double spends/DOS attacks can occur at much lower thresholds of hashing power than 51%. The bitcoin blockchain isn't exclusively controlled by miners either but split between miners and nodes with separate voting and separate powers granted to each. Indirectly developers, exchanges, wallets, and merchants have a large role as well.

Politically, bitcoin doesn't represent republics/democracy either because all users have ultimate veto power and can break consensus at any moment by forking or just choosing not to upgrade to new changes they disagree with(thus causing a fork). It is more similar to certain forms of anarchy in nature because of this quality.

Would you call I completely voluntary and open governance model that allows for any user(citizen) to instantly veto any change they disprove of a republic/democracy? The smaller fork has every right to call their currency bitcoin regardless of the majorities objections.