No wonder a tactical genius such as Eemes would highlight the crucial flaws in the strategy !
I dont actually know how to feel about the episode overall.
Like Stark mentionned, really disappointed that we get no explanation as to why the WW do what they do. Maybe we'll learn it in the coming episodes, but they Night King seemed too smart to me to just be plain evil without actual purpose.
The big tactical flaws were also really bugging me, as other mentionned before me (the crypt being safe, the Dothraki charge).
The death of the Night King is actually pretty fitting in my eyes. When you think about it, there was no "fair way" for the livings to defeat the deads, and if we know this, then so does the NK. His last scene makes sense, he thinks he has won so why hurry ? It's a common evil mistake but if we allow it in other creations, why not here.
As to why Arya was allowed to get this close, in that moment everyone thinks it's over, so the WW most likely have their guard down, and thus can just be surprised/taken aback by Arya appearing (she learnt how to move discretely). Now is the NK actually gone, i have no clue. I wonder if the mark he left on Bran doesnt work as some sort of Horcruxe, Harry Potter style.
A main character death would have made sense on a realistic standpoint (honestly Brienne or Jaime should have died), but there is still 4 more episodes. Let's just hope we're not going toward a lame happy ending.