Glad there seems to be consensus that that episode wasn't great. Personally I thought it was awful and highlights some of the flaws with GRRM's writing.
Obviously the story initially developed as a struggle for power over the realm, with the existential threat to Westeros in the form of the white walkers gradually supplanting the struggle for power. As a viewer/reader, you're effectively encouraged to look away from the iron throne and towards the white walkers, because struggles for power in Westeros are normal but this whole idea of the long night etc etc is, well, life or death. Then there's all of the lore that's bound up in it as well, all of Bran's creepy magic, the night king's ability to raise the dead. This then begs questions about the purpose of the white walkers, why they're after everyone, why it's so important to have Bran have these magical powers. We then went on these long detours into understanding them, being introduced to the children of the forest, the almost limitless chapters about Bran becoming the three-eyed crow etc.
So everything builds to this one moment. There's a protracted and tense battle. This comes after two episodes of sentimentality, with every scene effectively prefacing this massive clash. The battle itself ebbs and flows, but doesn't really amount to all that much. Then just as all hope is lost, there's some bullshit deus ex machina magic and Arya kills the night king and that's fucking it.
Literally hours and hours and hours of building to this. This is the first clash between death and life, the big battle, and it amounts to a bland and predictable result. Personally, I just left that episode wondering what the fuck the purpose of the entire white walker sequence was? As I said at the start, this story was the story at the end of the day, but it was dealt with as a petty irrelevance. No twist, no turn, no explanation, nothing particularly enlightening, just a boring predictable ending to it. Despite all of the lead up, all of the hype, the protracted and at times excruciatingly boring writing, despite all of the teases, all of the rhetoric around this as the biggest threat, it was just nothing? They didn't even sacrifice a single character of any consequence to the white walker story. Utterly meaningless.
Classic GRRM but on a grand scale. The reason his "trilogy" is now in its third decade of writing and certainly won't ever be finished is because he just can't help indulging stupid plot lines that make no sense and just waste time and effort. Sure, a diversion here and there is great (take the initial Stark v Lannister war, or Renly and Stannis...fantastic shit), but an entire plot within itself that ultimately means nothing is just ridiculous. Another good example is the whole Rhaegar's son Aegon (not JS) lives in the books, and the early invasion facilitated by Jon Connington....something billed in the books as a BIG thing and the focus of Varys' life's work, but ultimately so irrelevant that they don't even bother putting it into the show.
Hopeless.
PS: beyond the MAJOR plot issues, the cinematography absolutely sucked. Imagine spending that much on a fucking episode of TV only to have it impossible to watch because it was so dark. Sure, you can use dark to great effect, but probably leave that to the horror film people who actually know what they're doing??