Japanochina is what people want. Anything we produce will have as much to do with the diplomatic relations between Song Dynasty China and the Empire of Pagan as Tolkien does with iron age Europe. So? It's just a game - you make a good faith effort to provide a setting that plays well, and that means you preferably avoid and as-needed-retcon anything that makes readers cringe. A realistic setting grounded in history isn't what you want either, because it can't deliver a smorgasbord of your favorite tropes from Kurosawa and the Five Deadly Venoms. Once you've done that, the proper answer to the question, "can I play a Malaysian pirate princess?", is not, "sorry, we haven't done enough research to present the Maharaja of Srivijaya in a culturally appropriate way," but rather, "yes, you can."
A lot of what the gaming public wants is not necessarily what will make a healthy or even respectable setting. My point in illustrating the diversity of Europe was to show that even many European and US game designers cannot get this right or even care, and this will have an effect on any tabletop game being published with a non-Western mileau unless they do their due diligence beyond "hey is this pop culture anime/movie/etc trope hot shit?" Otherwise you'll end up with something approximating Weeaboo Art School Project, or the Asian equivalent of those foreign movies which presume that all of the USA is like Texas.
-Username17
Several things to address in your post. It's very easy and surface-level to adopt non-Western monsters willy-nilly for the cool factor. D&D does it all the time. But that's an easy street: monsters are often folktales easy to take at face value, made for entertainment purposes, or touch on some moral tale which relates to the dominant culture at hand that may not be readily obvious. There's also the fact that game designers in the West will still have a Eurocentric lens. If doing it for a typical fantasy setting, you run the risk of doing what Monte Cook did in making the Thunderbird an evil gog. Or statting out the Hindu pantheon in Deities & Demigods. The result is that you end up pissing off real people from that culture by giving a "kill Vishnu, get 1 million XP" message in your books.
Many Dungeons & Dragons settings have a Filipino vampire monster, the Aswang, but no Filipino-counterpart people. They have Persian monsters like the Lammasu, but no Persian-counterpart people. Or if they do, they end up coded as Arabs. By your desire to stick to cool monsters in an attempt to avoid recreating the classism/racism portrayed in existing settings is a false choice. You end up trading the desire to avoid one minefield and wander into another where you're willing to poach from the surface level of one culture but have no room for counterpart people of said culture in your fantasy game.
Delving into a culture, including its darker spots on history, does not necessarily equate to an endorsement. Rokugan, Arrows of Indra, etc got in hot water less for showing an unjust society and more due to portraying it as the natural order of things. Tales of the Caliphate Nights, an Arabian Nights-style setting, did a good job in this in noting that while religious repression, slavery, etc existed in 800 AD, the book overall painted it as an injustice even if was supported by the status quo. As for avoiding unintentional slurs, a cultural consultant/historian will help in this manner.
Secondly, focusing does not necessarily mean exclusion. Your Chinese Wuxia or Japanese Samurai game may have Filipino traders to the north and a Khmer Empire stand-in in the tropical south, but there will be less text dedicated to it. If our hypothetical setting picks up and gets popular, more sourcebooks can be made to further expand upon them. Kobold Press did this with Midgard: the German writer focused at first on Central and Eastern European legends and folklore, but over time with more articles/magazines/PDFs/etc he expanded his world into covering a lot more territory, including a Fantasy Africa counterpart the Southlands. It's impractical to try and write up an entire setting of a continent with 6000 years of history and one-third the world population in a single sourcebook. Starting off slow with certain areas, and working your way up, is better.
In fact, most of this thread has already focused on the Big Two Asian countries, and this does not necessarily demonstrate some desire for "racial purity" on the part of the posters. Just the inevitability that our limitations of literature and media will prioritize certain people and places. Nothing wrong with that in and of itself, just be mindful of it, especially when venturing out of that sandbox begins and ends at not-human elements from said cultures.
Tabletop gaming operates on a shoestring budget, and most of the funds go to artwork. The workload of ensuring that your not-Vietnamese, not-Korean, etc don't end up like the not-Norse and not-Slavs of typical D&D* will be a lot harder, even with cultural consultants, because the tales of civilizations we're less familiar with have not entered into the cultural consciousness. Most of us don't have that "lived experience" to draw from that we take for granted when talking about knights and wizards. This is doubly true in a design by committee game like this thread is for, unless the opinions of experts are prioritized over other posters.
*British/Japanese people with slightly different names
Finally, this is not to say that it's a losing battle. But that it's a whole different beast, and approaching it solely with a "rule of cool" without knowing the greater context can be foolhardy and you end up with another Evil Thunderbird.