Most Western CRPG fantasy settings - including Pillars of Eternity, Baldur's Gate, and Witcher - are a combination of High Medieval and Renaissance Europe, with the Witcher being closer to a strictly medieval setting than the others, but still the cities have a decidedly Renaissance atmosphere. Medieval settings not influenced by the Renaissance aren't actually that common - Diablo is the example that comes to mind, but the setting is all over the place, not restricted to Europe.
The early medieval period, defined as the time after the fall of the Roman Empire, but before the rise of stable Christian kingdoms in Europe, deserves more exploration in the context of fantasy CRPGs. The invasion of the Germanic tribes and their pagan gods, the loss of Classical learning and its replacement with a new warrior or barbarian ethos, the intense violence, superstition, and chaos associated with the age, etc. are all fertile ground for CRPG interactions, and are perhaps, more importantly, familiar enough that you wouldn't need to invent a completely different set of rules, as you would for futuristic settings, for example, and could still appeal to existing fans of fantasy.
The period between the 19th century and today is probably the most rare, when it comes to popular CRPG settings. It's not that it hasn't been tried - VtMB and Alpha Protocol are both examples - it's that it hasn't been very successful, probably because players associate modern settings with first person shooting games and stealth games, not CRPGs. It isn't easy, as such, to sell a modern period CRPG, because there are already so many modern period action and stealth games out there, that you don't actually fill a setting niche despite it being rare for CRPGs. Another setting that is explored often in other games, but which is relatively rare in CRPGs, is myth, either Greek or Norse. Again, games like God of War have put a virtual patent on such settings, so it's difficult to get people's attention with a CRPG set in the same world.
But I wouldn't say that setting repetition is the main problem with CRPG world building. The same period of history and cultural setting can produce works with vastly different tones. Lord of the Rings and Game of Thrones are both set in the High Medieval period, but is anyone going to argue that they create the same experience in viewers? There's much that can be done to make an existing setting unique and fresh. It is not necessary to set a game in the Stone Age just for the sake of being different.
Also, I would advise against thinking that the popular fantasy settings are popular only because alternatives have never been tried. The media turns to medieval fantasy time and time again because there's a recognizable cultural connection between these settings and the Western audience. Why don't we love samurai and ninja stories, the way the Japanese do? Why don't we love Chinese historical epics? Both of these traditions are immensely popular in their home countries - the equivalent of medieval fantasy for us - but when imported to the West, they attract a niche audience, at best. The fantasy market demands new and original settings every day, but at the end of the day, it's the European inspired fantasy that gets them every time.