It was no mystery that a lot of fans didn't like the final season of Game of Thrones, but nevertheless, it was said that everything that happened was how George R.R. Martin originally planned to end everything. Despite the fan reactions, Martin himself has said that he's sticking to his plans for the books.
Talking to Entertainment Weekly about his last A Song of Ice and Fire novels, Martin talks about how fan theories usually change stories, and how it won't affect how he finishes the books. He says:
"The internet affects all this to a degree it was never affected before… Like Jon Snow's parentage. There were early hints about [who Snow's parents were] in the books, but only one reader in 100 put it together. And before the internet that was fine — for 99 readers out of 100 when Jon Snow's parentage gets revealed it would be, ‘Oh, that's a great twist!' But in the age of the internet, even if only one person in 100 figures it out then that one person posts it online and the other 99 people read it and go, ‘Oh, that makes sense.' Suddenly the twist you're building towards is out there. And there is a temptation to then change it [in the upcoming books] — ‘Oh my god, it's screwed up, I have to come up with something different.' But that's wrong. Because you've been planning for a certain ending and if you suddenly change direction just because somebody figured it out, or because they don't like it, then it screws up the whole structure. So no, I don't read the fan sites. I want to write the book I've always intended to write all along. And when it comes out they can like it or they can not like it."
If anything, fans were actually fine with the direction the characters went, it was just the breakneck pacing that made all of the decisions feel unearned. Jon killing Daenerys has been littered in the books with the Azor Ahai prophecy, but having Jon turning on Dany a season after they just hooked up didn't have the emotional impact it should have.
When it comes to the delay, it was said that Martin already had an idea of how to end the book, but it was a case of writing how the characters got there. Showrunners David Benioff and D.B. Weiss apparently helped get the story across the finish line, but without the proper timing and character development, we got one of the most disappointing endings in TV history.
For now, all fans have are the final books, and Martin promises Winds of Winter should be done by the summer of 2020.