Then the writers either screwed up on the paladin's alignment and didn't changing it because then they'd have to rewrite huge swathes of lore, or they screwed up on their definition and understanding of feudal monarchy. Probably the vast majority of "Good" societies in D&D should actually be neutral, maybe with Good leanings. Radiant Citadel is actually a pretty Good society.
Also, "they suck so it's OK if we suck too" is not the argument you think it is.
I think you've missed my point.
Many of the older RPGers who post on these boards remember, and admire, Boorman's film Excalibur. It's a wonderful filmic retelling of the Arthur story. A key motif in the film is "the King and the Land are one".
I don't think anyone who watches and enjoys that film, or who enjoys the near-identical trope in LotR,
really believes in the theory of government that is being advocated. They are suspending their real political commitments and moral values to enjoy a romantic fantasy story, which works within a different value system.
The same thing happens when I watch an X-Men film or read an X-Men comic, and don't judge Storm for her failure to use her weather powers to relieve drought and famine. These are works of fiction.
To what extent they are purely escapist fiction, and to what extent they have something to say about the real world, is a further question. I think it is one we can set aside in this thread. The key point for this thread is that thinking onself into the Arthur story - a celebration of righteous kingship manifested through the pursuit of lethal violence - is no more or less absurd than thinking onself into a story about divine punishment inflicted on a people for its sin of pride.
These are all fictions, not documentaries and not treatises on actual moral conduct.
(Also:
@Vaalingrade has referred to the punishment of one man, but it's clear that the Cataclysm was a punishment of a whole people, not just one man. That's part of the trope - that the people participate in the wrongdoing of their leader. And in fact you don't have to look very far to find serious discussions that play on exactly this idea in contemporary scholarship.)