I'm not saying the last season was horrific like this one was. I just remember little clues that we were no longer watching the book play out.
For instance, when they all went on the expedition to bring back a White Walker . . . then they were attacked by an undead polar bear . . . no one important dies. Only unnamed "Ensign Gonna Dies" that you didn't even know were there with them until the very moment they were killed. I just remember thinking that it felt a little tv network-ish.
Let's not forget that in that same episode Thoros and Viserion also die, the latter being a huge deal.
Ya I am wondering what ole GRRM told them as guidance. Like did he say ya I got Bran winning the game the rest is up to you or did he say the rest of the Starks are good but the rest dies. Is there a lot more of the Night King that was just too much to have in the show? Also will the out come of the show affect how the rest of the book is written. We may never know.
I thought that they used his notes to help fill in the blanks for the final seasons. Undoubtedly there will be a lot more detail in the books as there always is (if he ever finishes them).