After digesting the implications of the last episode for a while I think it's fine. Not Brilliant, but fine. I wanted there to more to the story of The Other's but there isn't and that's fine. I had all kinds of theories about the Night King's motivations, but if it's just genocide, that's fine. He was a non character really, that's fine. Just a metaphor for an seemingly unstoppable force of nature. Fine. Not actually actively evil, just as uncaring as the wind and rain and snow. That's pretty good to be fair.
I really wanted there to be more to it. Some kind of ancient pact between the Children of the Forest and the First Men. There wasn't. The whole thing was an elaborate fake out. A subversion. I don't have a hard time thinking this might have been Martin's plan all along. He's on record in several interviews, stating that The Ultimate Battle Between Good And Evil doesn't really interest him.
I don't really disagree, up to a point. If anything I think the TV show probably showed us too much of the White Walkers and I'm not sure it was the best decision to give them an identifiable leader in the form of the Night King (who is not and will not be a character in the books). I think that the WW work much better as a looming threat and more of an unknowable, alien force of nature. I think I'm right in saying that in five (giant) books they've only appeared 'on screen' (as such) twice(?).
I do however think Martin's infamous quote about Dark Lords and Good Vs Evil is often misconstrued - I think he was just making a point in general about giving his characters and world a bit more depth, especially with regards to characters who might ordinarily be regarded as 'villains' (like Littlefinger and Jaime) - and to show the trials and pitfalls of ruling, and not just ascending to the role of ruler (and this is exactly what A Dance With Dragons is all about with regards to Jon and Dany).
But at the end of the day it's a fantasy epic and there absolutely
are characters in the series who are straight up, irredeemable Bad Guys - Ramsey, Roose, Joffrey, Vargo Hoat, Euron Greyjoy, Walder Frey, Craster, The Mountain et al and who ultimately need to be defeated by the Good Guys. And I still very much think that Martin's plan in the books is and always has been leading to some kind of a final showdown between the living and the 'Others/White Walkers', whether that takes the form of a war, or something weirder and more metaphysical (or maybe a combination of both).