Actually I'd argue that feudalism was the most egalitarian system mankind's ever had. Sure, Kings had it good but the difference between peasant and king wasn't nearly as wide as the modern gap between poor and superrich, nor the slave vs. emperor situation that preceded it.
Serfdom in which serfs were tied to the land might seem harsh today but it was lightyears better than what the poor had in Rome, which was slavery, and lightyears better than the lethally dangerous sweatshops (and yes,
more slavery) that followed in the "Age of Enlightenment." The serfs also generally worked less than we do today, amazingly enough. They worked around a 5.5 day workweek and had
30-33 days off for special feasts each year. That's a heck of a lot of time off considering the reputation the period has.
Wars under feudalism tend to be tiny affairs. Rome mustered 80,000 soldiers to attack similar numbers at Carthage. 10,000 would be a vast army in the middle ages, with many armies being in the hundreds. The battle of Agincourt was one of the largest in the middle ages and it pitted 36,000 Frenchmen against 9,000 Englishmen.
During the middle ages things things like the Peace of God and Truce of God forbade civilian deaths and while there were breaches of this, on the whole it was kept. Comparatively, when Rome went to war with Carthage, Rome went to war against
all Carthaginians, man woman and child (and in some cases even pets) were to either die or be enslaved, there was no "civilian" in their minds. And then after Feudalism we got the delights of World Wars and industrialized warfare.
Ultimately feudalism has one all-defining virtue. Feudalism in general is the exact opposite of tyranny, the monarch's power is greatly reduced compared to other governmental systems with said power being split between innumerable aristocrats, nobles, and minor nobility right down to the equivalent of the town mayor. the system of obligations prevented the King from doing too much and sharply limited his influence, with the result that the power flowed downhill compared to other systems. This distribution of power hoses any attempt at really wresting control from the local people and makes for an extremely level playing field compared to anything else mankind has tried.