I think you're overlooking the ideological aspects of the war, which did on the whole entail putting democracy (except Russia) versus autocratic militarism and then Bolshevism.
In any case, the point of having the triangle is to display ideology, not alignment. A country could be democratic, and still not be apart of the Entente (USA up to 1917) for example. Therefore, the triangle must remain a representation of ideology rather than diplomacy, thus necessitating the use of symbols like Marianne.
Furthermore, it is suitable to favour displaying the ideological over other aspects as this shows what they felt that were genuinely fighting for. It's correct for the time period, at least.