I don't think centralized hierarchical structures are compatible with Epicureanism. Self-suficiency, being an epicurean virtue, is increasingly stifled the more centralized and top heavy power structures becomes. I also don't agree with your analysis of the decline of epicureanism in late antiquity, from what I've read most scholars think that in the face of environmental and societal changes the appeal of Epicureanism to the general populis declined.
What was so special about the social and environmental conditions in the centuries when Epicureanism was popular as opposed to those when it declined? Nothing much really. It was the same old agrarian society. In any case Christianity and Islam have survived plenty of devastating social shifts and the same should be demanded of any successful creed aiming at the hearts of as many people as possible.
I agree that modern (and ancient) forms of social organization are not compatible with Epicureanism just as for example a modern Western democracy is not compatible with Islam although it's perfectly possible to live in one as a Muslim and be well-adjusted.
Non-hierarchical forms of social organization are known to be indefinitely viable only in the case of immediate-return hunter-gatherers which today can hardly be said to exist anymore. They represent way less than 1% of the global population. All other egalitarian experiments from within civilization have failed and in the rare case where they were politically successful (starting with revolutionary France) produced nothing more than mass terror and hideous dictatorships. In my view civilization and egalitarianism cannot possibly co-exist and that's why even numerous non-political small-scale egalitarian experiments in the West have failed too. It's not that they were destined to fail, it's just that civilization does everything in its power to destroy such communities and it invariably succeeds because it is resourceful, aggressive and ruthless. It is no accident that resourcefulness, aggression and competition have always been civilizational virtues. It is precisely those traits that civilization needs to sustain itself. Christian theology understands this dynamic too in its own way. That's why Jesus calls the Devil 'the master of this world' in the Gospel of John. Civilization is in a certain sense truly the realm of the Devil. It requires the destruction of our souls and feeds on the darkness in our own hearts. In this world it is not wise to attempt egalitarian experiments. The master of this world will soon come after you and crucify you.