...and because I consider it rude to answer to posts with a one liner, permit me to address your points one by one.
As Eldritch Lord noted, I'm not arguing that medieval Europe is simplistic. I'm arguing that it isn't D&D.
No one said it is. I address this in my previous post where I mention your name.
You have knights, but they don't act as a vassal to a king in any of the standard settings.
Not always but there are cases they do. Take a look at the Purple Dragon "Knights" who serve under Azoun in Cormyr.
Whether they literary serve a king or not does not make them less medieval-ish.
What about the Knights of Solamnia in Dragonlance? Are they less medieval-ish?
They act as vassals of "the Oath and the Measure"
Even the real knights of medieval Europe were "supposed" to serve goodness and high ideals... their king was "supposed" to uphold those ideals.
They don't have a fief and they don't lord over serfs. Yes, that's not all there was to the dark ages or the later medieval era, but it's not in the basic settings in any real way.
Not in the basic settings and not in any campaign I've ever played in!
I suggest you read the 3.x Forgotten Realms Campaign Setting, from page 80 to 83...because thats EXACTLY how things work in the Realms. Feudalism... the high clergy has political power... 90% are peasants/farmers striving to survive while working the lands belonging to the nobility, just read it.
The same thing holds true in DragonLance, and I know that for I have DMed 2nd edition DragonLance for a few years... Can't give you the references for I only have the books in hard copy and not with me. Still I can tell you for a fact that there were statuses included for every PC/NPC... from slaves and commoners (farmers) to noblemen and royal rulers... land ownership playing the exact same role.
Also, Dragonlance includes another Medieval-ish cliche, for the main campaign based on the starting trilogy begins with no deities, for the Gods have turned their back to the world... The people have sinned, they ask for forgiveness... chaos everywhere blah blah blah...
That's what happened in real life as well, for when Europe was closing to the year 1000, people were preparing for the end of the world, (Millennium was NOTHING compared to the superstitions of the time). They thought they had failed their god... chaos and violence was rampant...
Having played in Greyhawk campaigns, both 2nd and 3rd edition, I don't remember it being any different...
Greyhawk City is flat-out Renaissance
I don't know what City of GreyHawk you've played in. The one I 've played in was a rich and flavorful Medieval-ish Capital, with all the guilds and merchants, the nobles and the craftsmen... everything one could find in an actual Middle Ages Capital. Don't get this wrong again... It WAS NOT a Medieval Capital, because of magic wizards, clerics etc... still it WAS BASED on a medieval Capital more than any other Capital from a different historical period.