Perhaps I'm oversimplifying things, but I have personally always assumed that using "Medieval" to describe D&D was almost entirely a reflection of the (non-magical) level of technology, and not anything societal or cultural.
Interesting. The article does mention the aspect of tech/weapons to mention it's not particularly "medieval" either:
> The D&D weapon list has a medieval feel to it, but partly that’s just because that’s what we’re expecting to find. In fact, it’s a sort of survey of (mostly) pre-gunpowder weapons. Most of the weapons and armor appear in ancient Europe and in Asia as well as in medieval Europe. Partial exceptions: Composite bows are mostly non-European, while longbows are associated with Europe. The halberd is basically a Renaissance weapon, and the two-handed sword appears in medieval Europe, India, and Japan, but not the ancient world. No one knows what “plate mail” is supposed to be.
Early D&D didn't really make any sort of assumptions about technology level, either. Arneson's campaign was heavily implied to take place in a post-apocalyptic future - Blackmoor was full of advanced technology, including nuclear powered flying cards, lasers, androids, etc.
Gygax himself didn't lean into it as hard, but there were plenty of fairly gonzo modules that did include aspects of future and/or alien technology.
Wouldn't that lend credence to the author's claims? That it only appears to be a medieval society, but is instead something very different (a liberal capitalist world after grand social dissolution). After all, the two adventure/roleplaying game series that Bethesda is/was known for are The Elder Scrolls and Fallout, the latter, at least, explicitly taking place in a post-apocalyptic universe.
I think the discussion itself is kind of a weird one to have. Most of the author's point is about OD&D, but OD&D itself was a very short lived phenomenon. People pretty rapidly moved to either the AD&D or B/X line of products, and there are some departures in the rules, and both lines added official rulebooks that do explicitly contain things that go against a lot of the author's points. And basically every table from the start has had a pile of house rules (or at least generalized processes) to handle situations not explicitly called out in the rulebooks. Much of the question of feudalism is more of a campaign setting question than a rules question - plenty of people played campaigns back in the day in settings where there was royalty, where you would have to purchase or otherwise acquire land rather than just plopping down your claim somewhere.
The argument the author is making is messy because it mashes together the dichotomy of old school D&D versions vs. the modern equivalents. Originally, D&D was a framework that you built on top of. You might adhere fairly closely to the rules as written, but they were intentionally quite basic in nature, and additional structure and systems almost always came as part of your campaign milieu and table-specific needs. Modern D&D has significantly more rules - it's a more complete game, with all the good and bad that entails. Neither have a mechanism to force you to use any specific portion of them, and many people don't.
I agree with the sentiment that D&D is not pro-medieval, though depending on which rulebooks you use it might incorporate aspects of medieval society and structure. I also don't think it's anti-medieval, because that implies structure that isn't there. Any given campaign or table might be more or less medieval than any other and still be totally authentic D&D.
There's a company that is famous for two series, one is a fantasy roleplaying game, one is a post-apocalyptic role-playing game, but the story and the structure of the games are nearly identical and the in the latter the mechanics and gameplay make a lot more sense in the context of the story than in the former.
