I also loved it. I guess if you're good enough you can do anything. But yes, I also found the characters often pretty flat, especially in the third book. Still, read them all, and found them quite refreshing.
As for the cultural barrier: as a cultural anthropologist, I would argue that sure, there might be such a barrier, and you might miss things as a reader if you're not Chinese. On the other hand, you'll most likely always miss hints and context in books to some extent: either because the other is from a different country, language, county, city, different gender, age, rural or urban background, has a different profession than you, or a different job, or a different opinion.
Or, as David Graeber (2015: 28) phrases it:
"What’s more, if one goes slightly further and argues not just that reality can never be fully encompassed in our imaginative constructs, but that reality is that which can never be fully encompassed in our imaginative constructs, then surely “radical alterity” is just another way of saying “reality.” But “real” is not a synonym for “nature.” We can never completely understand cultural difference because cultural difference is real. But by the same token, no one Iatmul, Nambikwara, or Irish-American will ever be able to completely understand any other because individual difference is real too."
Anyways, that's why I wouldn't put too much emphasis on the cultural barrier.