One thing to note is that medieval political arrangements were actually a lot more varied than most people believe. We in the modern world tend to think that autocracy is the default of human political experience (e.g. humanity went from absolutist pharaohs to absolutist emperors to absolutist kings), but that is a mistake. In medieval Europe, there were certainly feudal monarchies, but these were not absolutist regimes: the nobles in particular were especially powerful, and in fact 'feudal' in scholarly circles is actually synonymous with 'decentralized', 'politically fragmented', and sometimes even 'anarchic'. Furthermore, feudal regimes were by no means the only ones around. In early medieval Europe, tribal associations led to generally weak kings, with local communities having a big say in things like justice and court cases: literally, it was the 'good men' (boni homines) of the community that rendered judgment. In the cities of Italy, from the eleventh century on, communes prevailed, hearkening back to the old Roman Republic (and at times trying to resurrect it). Their political systems were highly varied, even if, at times, they did become dictatorships. Consider also Iceland, which had essentially no central government (apart from the Allthing), and was almost an anarchy. The papal states were a theocracy, but the theocrat was elected by the local clergy (at least after the Gregorian Reforms and invention of the college of Cardinals). Towns in general often had a great deal of independence (even outside Italy).
All of this is just to say: even in 'feudal' societies, politics were often rich and vibrant. Absolutism and totalitarianism are rather recent inventions, and shouldn't be imposed upon medieval culture. The example of King John shows what could happen when the king tried to trample on the customs of the community and the privileges of the privileged.