Then why'd you bother to read the last couple in Mereen? No way in hell that plays into the final ending at all?
Or, it matters about as much as the entire crown game does: gets the characters the experience and into the place they need to be at the end.
Seems like it works to me, as the entire series started with the white walkers, they've been looming the whole series, and we've gotten repeated warnings to stop dicking around in the south and focus on the real threat. What kind of retarded series would it be if it DIDN'T end with them figuring out that the stuff down south didn't matter, needed to be resolved so they could focus on the real threat up north? Everything has built to that.
Having the political backstabbing end up being more important, and having the walkers just turn around and lose interest would be the real pointless letdown. After the buildup, that HAS to be the final conflict, no? Not who maneuvered who into marrying whom...