Why are we still stuck in this era?
I mean, not that I’ve ever seen a fantasy work that accurately portrayed the Middle Ages, regular cleaning/bathing rituals, advanced is art, music, and sciences, and all, but still, why? What is so interesting about it? There are most of 20k years to draw upon for roleplaying inspiration before the advent of the cannon, across the globe.
What is so interesting about the (very much pseudo) medieval tableaux that keeps the community stuck at that well?
I'll see your point and raise you one: Why are we stuck in Earth analogs? Not all settings, of course, but the vast majority--at least of kitchen sink settings--just do the old re-hash of "fantasizing" Earth cultures.
I realize there are reasons for this. For one, it is easy--both to design and for having a mental picture. The corollary is that it is very difficult to come up with new cultural forms. Another reason is that it is, well, just a game. If you want to create a unique piece of art, that's one thing, but if you just want to have fun and play a Nordic barbarian or an Egyptian sorcerer, it is nice to have that option.
I'm also not suggesting that there's anything wrong with using Earth cultures as inspiration, even a basis for original creations. It just doesn't have to be wholesale.
Tolkien's Middle-earth is a great example of how it was obviously influenced by European--especially British--folklore and history, but he still managed to create new and distinct cultures and histories. Gondor is not any particular region or time in Earth's history (or rather, it is roughly supposed to be Europe circa 4000 BC, but in a loose sense - but that's another topic). The closest to a one-for-one Earth analogy is probably the Shire, which is pretty much a humorous and self-deprecating take on rural England. But Middle-earth shows us how you can make an entirely original setting that is inspired by our own cultural traditions and history, but feel fresh and distinct.
As an aside, I've been doing a lot of research on historical population figures and exploring the idea that a lot of setting designers, published or not, play with the erroneous assumption that fantasyland has to be Medieval. In many cases of published settings, it clearly isn't. A lot of settings are spread out across equivalent historical analogs, and the center of gravity is often not Medieval (Europe), but closer to the Renaissance--even the early Modern Age (1500-1800ish).
Another fallacy is the idea that magic is only used to cast spells while fighting other wizards or seeking treasure. If magic is really as ubiquitous as it is in most D&D settings, why hasn't it impacted societal structures more? And why aren't all national rulers wizards? A "realistic" fantasy world would probably have more magical infrastructure, and the default rulership model would be a kind of arcane dictatorship, benevolent or not. In that sense, Thay may be the most "fantasy realistic" nation in the Forgotten Realms. A world-builder could even use such a magical dictatorship to justify fantasy Europe: maybe an order of wizards rules the land, and maintains tight controls on it by essentially keeping the sheeple stuck in a Medieval context (i.e. magical feudalism).
Or, at the least, why not consider these ideas? I agree: fantasy Medieval Europe is stale. But I'd go further and say that excessive Earth analogs are stale in general. Meaning, I don't think the only answer is to do fantasy India or fantasy Mexico (although it could be, but that's been done a fair amount already). Or, at the least, if you're going to do fantasy Aztecs, really explore the ramifications of the presence of monsters and magic, and feel free to improvise off the analog, not just re-hash it.