We just finished re-watching all 8 seasons of Game of Thrones. We all know Season 8 was terrible, but the Long Night (the battle of Winterfell) is the WORST. I want to talk about what a terrible commander John Snow is.
Firstly, the humans should have had unbelievable reconnaissance via Bran flying ravens everywhere -- what else did he need to do while the Night King advanced??
Secondly, given this amazing intel and air superiority, John and Dany should have been running strafing missions constantly. You're worried about the Night King and his AAA? The army is miles long and you've got great intel. Attack where he ain't! And come in low.
Thirdly -- it's been well established the dead don't have ranged weapons (think John and the others on the island in the middle of the frozen lake). And John's cavalry has a decided advantage in speed. So use your intel, deploy archers along the route, put a few thousand dragon glass arrows into the army of the dead from a safe distance and bug out. Wash rinse repeat.
Come to think of it, the Dorthraki have mounted archers...
But here's the biggest failure. At one point Bran tells them that the Night King can sense where he is and is drawn to him. So John should have Davos smuggle Bran into Kings Landing! Let the Night King march on Cersei Lannister and then we'll see if she thinks the Army of the Dead is real. Don't want to send them into the biggest city in Westeros? Ok, hide Bran in Casterly Rock. Tyrion knows the secret entrance. Whatever you do -- KEEP BRAN MOBILE and use your intel, ranged weapons, air superiority and massive mobility advantage to win a war of attrition.
This leads to another pet peeve. There's not a lot of (good) military strategy or tactics in sci-fi/fantasy. Good examples are Ender's Game, The Forever War, Chronicles of Thomas Covenant, Dorsai...