I'm also not convinced that the storyline shouldn't have been reversed . . . Dragon Queen vs. Lanisters first, then move on to the Night King.
Again ... "Winter is Coming" has been the black cloud hanging the whole series while all the politics of squabbling men play out. Feels like the real threat was handled already, and then they have circled back to just another human battle over power.
I disagree. It's Game of Thrones not Game of the Night King. The most important story that has run throughout is who is going to rule, who is going to win the game of thrones.
I always interpreted this to mean more than the weather. That it was about the White Walkers and the complete upheaval of life as they knew it because of the constant threat of eradication.
Maybe I'm wrong, but I wouldn't think the arching storyline would be only about dropping temperatures.
It means many things. It's the Stark motto. It literally means that the long winter is coming (which are particularly harsh and dangerous for those in the north). It is also a metaphor for the dangers that come with the darkness and the cold, including the Night King and White Walkers, but isn't exclusive to them IMO.