Alright everyone I'm back. Let me start off this by saying that if you believed Episode 3 made sense narratively then you weren't following the story well. After episode 4, I understand what the show did. This will be decently long but the TLDR is: The Long Night is the true ending of the show and they changed it for $$$.
The ending makes sense if you work back from this key point. The reason nobody could die in episode 3 and it felt like EVERYONE had unreal, jarring plot armor is because... they did. That was because they COULDN'T die because that fight wasn't supposed to happen yet. That battle is supposed to be AFTER the battle with Cersei (Or more like Feagon in the books as it would be a Targaryen invading westeros led by the true King Feagon (a Blackfyre loved by the people and makes Dany going mad make way more sense as she is effectively an usurper)).
Why was Tyrion an idiot and "trusted" that Cersei would send her army when she OBVIOUSLY was not going to and it felt forced? Because there was no army and there was never a stupid plot of going beyond the wall to get a wight to show to her. None of that actually happens but it had to in order to change the plot from the real story. Cersei is dead and her armies were dead before that long night coming up in these episodes. Wouldn't it make more sense for Jon (or Feagon) to Unite the Seven Kingdoms after everything with Westeros happens? Uniting the realm against a singular threat after being shown to be the true ruler.
The show runners did not or COULD NOT create the final the way it was supposed to be with the Long Night. But guess what HBO is doing? They're creating a prequel about the white walkers..? That's weird isn't it? Why would you do that after neutering that entire storyline seemingly out of nowhere? Because its the actual ending they'll repackage to milk the GoT cash cow. Yes, the Arya storyline of her killing the NK felt JARRING and out of place, that's because it was. It was done for money/time management reasons. If you work backwards from this theory, the entire story falls into place (as much as a TV show with a budget can).
We can discuss this more after the series is over. I think people will start to jump on board with this theory as we finish out the show. Remember, think BACKWARDS from the idea that HBO wants as much money as possible because... they do. Why wouldn't you carve out a huge part of the story (the ending), repackage it, and serve it back to the viewers as "DLC" ( like Mass effect 3) for the real ending?
Think of Episodes 4, 5, and 6 to be the 1st, 2nd, and 3rd episodes. Also, remove any of the whiter walker storylines happening the past 2-3 seasons and episodes 1,2, and 3 not happening yet. Put all of the Great Other plotlines near the end to AFTER these final 3 episodes.
TLDR: This is the "real" ending before the Long Night. Watch this as if the characters are the characters from the books with all their powers (Book Euron can DEFINITELY kill dragons).