I don't think that the final season of HBO's Game of Thrones ruined the entire series but I do think that the final episode tried and came close. If we assume that all of the events came from GRRM, which I doubt, GRRM will have some heavy lifting to do in his final books in order to make these plot points believable.
The idea that people who know nothing about Bran other than he is Ned Stark’s son, “fell” out of a window, and has a creepy personality would accept that he should be king, based on the word of a patricidal dwarf known continent wide as a drunk and whoremonger, makes no sense. This "best story" justification is crap. Everyone has stories.
That these same people would tolerate the North going independent boggles the mind. If Bran’s own sister won’t bend the knee to him, why would anyone else? Every region was independent before the Targaryen invasion, not just the North. The Iron Islands and Dorne are just as culturally, religiously and ethnically distinct as the North is. Having the entire continent be ruled by Starks AND the North be independent seems like too many bites at the apple, even for a Stark bannerman such as myself.
Grey Worm and the Dothraki likely outnumber other Westerosi forces in and around King’s Landing at the time of Daenerys’ murder. If not then it’s a close call. But Daenerys JUST gave a wildly popular speech promising permanent revolution and worldwide conquest to her soldiers, who LIVE for such things. Daenerys has also condemned Tyrion to die.