Who was managing the defense anyway?
Jorah went with the Dothraki. Jaime was on the front. Jon and Daenerys were flying their dragons, Tyrion was in the crypt with Sansa and Varys and Theon went with Bran.
Other than that it was just lone wolves like Clegane, Beric, Arya, the Unsullied and Brienne out there.
The only "tactician" who was in the back to manage the defense of Winterfell was ... Sir Davos. And he performed as well as he did during the battle of blackwater bay.
Failing the one task he had which was signaling the dragons.

They could've at least put some catapults behind the castle walls instead of neatly lining up their entire army outside of the walls ready to be slaughtered by a zombie horde.
Another strategic error were the use of the dothraki. They should've told them to hold and wait until the enemy forces got closer and attacked them at their right and left flanks. Much like how Stannis easily routed the Wildlings.
Davos is supposed to know all this.
