As for democracy "These sorts of societies propagated for hundreds or even thousands of years in antiquity just fine" - I don't know of any that practised the consensus driven democracy that almost all these proposals use. Ant if you're reaching into antiquity then not even normal democracies. Unless you're talking about a Athens with their slaves and adult male citizen population having a vote. In which case sure, I can get behind that but that's not what those spaceship designs propose. They all assume all decisions will be unanimous and no one will ever break the law.
In actual fact history proves the opposite and all exploration and conquest is driven by strict hierarchical organisations and the idea that you can fly a spaceship across light years without a captain who can condemn people to death is laughable.