Big gripe for me is that NK should not have been Arya's to kill. It feels like they tied up loose ends with the wrong threads. Arya's training should have been building to her getting the revenge for the Starks on Cersei/Lannisters not the Night King. That should have been Jon's destiny. He and the Night King were intertwined and instead we got Arya handling it, after just seeing him for the first time
IMO it would have been cooler for Arya to avenge/save The Hound by killing the Mountain with the cool dagger drop and set up any of a number of more meaningful people to finish off Cersei - Jaime, Tyrion, Sansa, Dany, etc
They went for the surprise factor since Jon killing him would have been 'obvious'. Jon's dying and resurrection definitely does not really makes little sense now.