The ending is in the unreleased George Martin's book
George Martin didn't complain about the tv ending, assuming that's the book ending too.
We can't complain too much about that.
But I do agreed that the pacing of the story seem a bit rush. HBO have agreed to purchase the full 10 episodes for season 8 to properly conclude the ending.
I guess the directors can spend a bit more time finishing the loose end that was tied up weirdly.
For example, Bran claimed to be the 3 eye raven, and everyone quickly assume that was true. Audience knows it true because we all saw the development, but other characters themselves didn't see any of that.
I wish the 3 eye raven power and the leadership of Bran was shown more, considered nobody challenge Bran for the kingdom when he was declared king of 6 kingdom.