To share my thoughts on this season more generally, it's not good, and this last episode was particularly weak. The show at this point is little more than spectacle. It's no longer about the sharp writing, interesting characters, and powerful themes, but about splurging on their excessive budgets and showing off what they think looks cool and impressive. There's no reason why an episode centered around a battle can't be every bit as smartly and tightly written as an episode centered around political intrigue, and I'm not going to cut a show that I know is capable of so much more any slack for this kind of moronic writing. What the fuck was up with the Dothraki charging ahead of everyone and completely wiping themselves out like that? It's a rhetorical question, as I know perfectly well the answer is nothing more than the people behind this episode really wanting to have a scene where the lights all ominously flicker out and impress upon both the heroes and the audience how fucked the situation is, but that dramatic moment comes at the expense of common fucking sense. That's not how battles are fought. You don't "use up" the divisions of your army one at a time like that, because then they aren't there at a later point when you really need them. The people behind the show know this, because battles in the past were shown far more realistically than that. And like gary said, it was definitely intentional. Jorah led the charge, and there's no sign of any dismay from any of the mains until the lights start flickering.
The article crutonius linked explains most of my other issues with the stupid writing better than I could, but you don't need to be a military expert to be exasperated by the nonsense we saw. Why did they march out in front of the castle, negating its defensive advantages? Why did they dig a trench behind them? Why did Jon and Dany spend more time on dragonback bumbling about lost in the fog than actually attacking the enemy? Why did Bran decide to zone out for the bulk of the battle? Also, and this is more of a narrative issue, I found Arya stealth-killing the Night King to be kind of anticlimactic. There's no real connection between the two characters, beyond one being good and the other bad. He wasn't her villain, put simply. It's like if, say, Sam ended up killing Cersei. It wouldn't make any sense from a dramatic standpoint. On a more positive note, though, Arya's stealth section in the library was genuinely great, and the subplot with her and the Hound was arguably the highlight of the episode.
Also, I'm glad the Mormont girl is dead. She was a joke (haha look it's a young girl talking like she's an experienced, no-nonsense military commander) that was fairly amusing at first, so the writers felt they had to repeat the same joke fifteen more times.