They can close at least one of the bajillion different plots that opens up during AFFC and ADWD. I mean, there's a lot of huge potential thins to choose for a "grand finale" that doesn't involves massive CGI battles:
- Cleaganebowl or at least, the laid out of the trial by combat
- Stannis and Ramsay's fates
- Jon's resucitation
- Danerys moving towards Westeros
- Sansa's ladyballs dropping
- Brienne's endgame
But no, better end every single plot into a retarded cliffhanger in order to prevent this season to have any kind of climax or resolution. Masterful storytelling, that.
They could do most of that, but won't do any of it. Hell, they can't even be arsed to give closure to characters like Gendry and the BWB.