The dichotomy is this: Train To Busan is a quintessentially South Korean film: trains and travel and family and distance mean something entirely, uniquely, to South Korean culture.

However, it succeeds far beyond where it ought: it is a South Korean movie loved by people--me, perhaps you, who not only have never been to South Korea, but who don't even know anybody who has--that succeeds far beyond its remit: it is a fantastically well made film that, rather than being insular and encapsulating is, in fact, generous in its mix of the particular and the universal: finding where South Korea is identity apart, but where, also, identifying with a far larger audience.

The very fact that it can find purchase beyond its scope IS the very thing that makes others think they can remake it...

But your argument is that Hollywood can't make that kind of film. And, I think you might be right. The closest it has come, as you point out, is The Departed, which finds commonalities with Infernal Affairs (and, truth be told, I could not tell you which is the finer film). But The Departed grounds itself deep with the particulars of a certain past and passed Boston/Irish amorality in lieu of the absolutely unique cultural stew that is the Hong Kong of Infernal Affairs, making it less a remake and more a reworking, that doesn't speak much with the original.. .