I think they just totally fucked up the ending plot sequencing entirely. They could have structured the past two seasons better to allow for a more dynamic and interesting ending if they had fought off the first major invasion of the white walkers, but not kill the Night's King (maybe have him flee on the ice dragon?) Then do all the political Kings Landing bullshit while 'Winter' starts to starve the seven kingdoms, then have Jon and Co leave with Dany on the throne to go North to 'end' the Winter.
Then you could write whatever ending you wanted at that point. Jon, Bran, Sam, Ghost, Tormund, and a few others go North to kill the Night's King. Bran has to stay in the Land of Always Winter because reasons, to hold the Winter at bay for a time. Dany goes psycho after Jon leaves and the other lords turn on her/abandon her? Cersei and Euron regroup their forces to attack Dany, then Jon comes back (maybe even riding the fucking ice dragon) and pwns everyone before having to save KL from Mad Dany? That's a way better flow of events than what we got, while achieving the same basic thing. The way things are going now, with the white walkers already defeated, there's no reason for Jon having to take the black at the end of the series, which is always where it was heading from the start.