I mean, this is like saying "because DND has magic, and the real medieval age didn't have magic, that means DND is anti-medieval". It can be accurately described as "medieval" without replicating every element of actual medieval society. And there are enough medieval like elements in there that it strikes as a sufficiently resonant descriptor for me.
I did read it :) I disagree that not being feudal is enough to disqualify something as medieval. Loads of DND components are medieval, the timeframe, the architecture, the technology (excluding magic), the vague element of religion like cleric/etc. It's like a very blurry view of medieval times, with certain elements dropped out. But not enough elements removed to say that it's not based on medieval times; let alone anti-medieval!
