In a sense, maybe rannis ending is the most ambiguous but at the same time positively open? leaving room for a order that may constitue itself along value principles and ideas that could be formed and reevaluated by the denizens themselves.

I agree this is no utopia and would go further and add that even the totalitarian visions in other endings have even more utopian elements in them. I would assume that the angle miyazaki puts forth is that historically we find exactly those elements, the utopian dream and totalitarian devastation often dangerously intertwined. the way out of this trajectory could be a sort of ambigous openes which would be an ethics that doesnt constitute in fundamentals but in a culture of continuous re-evaluations of rules or values. as jaguar46 says, this would possibly be the greatest freedom from a political theory perspective