The inactivity of the White Walkers in the battle
IMO, that episode could have used a few scenes of Brienne, Jorah, Beric or the Hound going one-on-one with the White Walkers, just to break up the incoherent zombie action (just like “Hardhome”).
Instead, for whatever reason, the White Walkers only appeared briefly during the final battle before being destroyed.
Weird creative choice.