Since the topic requested musings, I'll oblige...
One of the reasons that Mystara is cited as a setting that WotC probably can't revisit is that many of the nations in Mystara hew a little too closely to the "real world" for comfort. Much virtual ink has been spilled on the Broken Lands supplement "Orcs of Thar" and how a lot of people find the content of that Gazetteer racially insensitive for modern gamers, but let's set that particular element of the setting aside for the purposes of this musing, please, because that's its own separate ball of wax.
Many of the "human" nations in Mystara are fairly obvious analogs of real-life fantasy cultures - often amalgams of several cultures. For instance, Karameikos' native elements (the Traldarans) have many Slavic analogs (though I see many of the names in Karameikos and they are clearly derived from Hungarian names, and Hungarians aren't Slavs, but you get the idea); Thyatis is the Byzantine empire (though careless players will probably see "Ancient Rome"), the Ylari mirror aspects of middle Eastern culture, the Northern Reaches are clearly Viking-inspired, the Ethengar Khanate reflect steppe nomads like the Huns, the Magyars, etc.
Mark Rosewater (head designer of Magic: The Gathering) did an article on lessons in game design ten years ago called "20 Years, 20 Lessons" (
Twenty Years, Twenty LessonsāPart 1 | MAGIC: THE GATHERING) and two of the lessons that I think is useful here is Lesson #3 "Resonance is Important" and Lesson #4 "Piggybacking" - the quotes I think are relevant here are:
"Your audience has a deep deposit of emotional equity in preexisting things. As a game designer, that's a tool you should make use of and build upon. This lesson is that some of your tools come from the players themselves."
and
"Piggybacking is a term defined as "the use of preexisting knowledge to front-load game information to make learning easier.""
Last time I ran a campaign, I ran it in Mystara - Karameikos in particular. My players were young (college age) and brand new to D&D. After a couple of campaign sessions, one of them expressed something to the effect of, "I get the political tension here; the Thyatians are the Romans trying to assimilate a conquered people ... the Ylari guy we just met; he's kind of like Arabian, and that's why his customs seem so different from everyone else's, right?" This might not have been politically correct, but the real-world analogs allowed him to quickly understand the setting; I hadn't explicitly pointed out "the Ylari guy's customs are different" I simply said he brewed up some coffee and offered to share it while he and the PCs discussed matters (I said it as though it was the most normal thing in the world) but remembering that in the previous session, there were suspicious looks in the tavern when a Thyatian walked in, and everyone in the tavern ordered ale, the detail of "coffee" was enough to make him realize this was a foreigner and they needed to be mindful that his customs - and motivations - were different than other NPCs'.
So I guess my musing is that the parallel to real world culture can be a trap if done poorly, but if done correctly can very quickly enrich the world of Mystara. Make sure you're getting the "enriching" version.