Well having eastern / muslim (in exceptional cases) tech groups being able to regularly and relatively easily westernise is all right but when 3/4 of india and subsaharan africa is westernised by 1600 that's probably not the most realistic (of course the last time I checked and noticed that happening was a couple of versions ago so they might have fixed it)
I find it much, much more unrealistic when states that have been peacefully neighbouring modern states for decades make no attempt to modernise. Japan and China are special cases due to their xenophobia, and subsaharan Africans didn't really organise civilisation the same way the rest of Eurasia did, but I find that demographics syncretising with modern ideas usually modernised sooner rather than later. Really, people say only Russia westernised, but they forget about the Cherokee, and about Japan — the Meiji restoration happened a measly five decades after the end of EU4, who the hell can say with certainty that it was
physically impossible for Japan to experience similar conditions beforehand? I find it more likely for them to westernise very soon after the Westerners show up than I find it for them to convert to catholicism — and I find it downright
unlikely that a catholic Japan wouldn't westernise.
As for Africa, though... a lot of their populations aren't westernised to this day. Their government is western, sure, but it's not particularly effective most of the time. I'm not sure how you'd model that in a video game.
edit: Also, in modern times, east-Asians have shown a remarkable ability to adapt and modernise. Look at Singapore — a beacon of high-tech capitalism in a black sea of Islamic xenophobia. Its population? Mostly Chinese. Now, why would this not happen sooner, were the Son of Heaven deposed?
