Martin knows prose. His expertise of Voice is incredible; that's what made the series such a hit with fans and critics, delighted to have gritty, realistic epic fantasy.
Unfortunately, somewhere between 2000 and 2011, Martin forgot what the hell it was about. The first book had a cohesive story; sure, there were cliffhangers for future volumes, but the story was entertaining. Book 2 was forgivably dry in the way of middle books for trilogies everywhere: Too much setup, not enough resolution. Book 3 rectified, it was delightful.
Then came The Change. Martin originally released a book 2-3 years, but it was 5 years to book 4, another 6 years to book 5, which were originally supposed to be one book.
Why were they so long, and why did they TAKE so long, compared to prior volumes? Martin's unwillingness to cut, which he has admitted. Fair readers, if you ever see an author UNWILLING to cut, run. Save yourselves.
Martin split Planned!Book4 down the middle by character, giving fans their least-favorite characters in the book they'd waited 5 years to buy. To get more of the characters they wanted, fans had to wait an additional 6 years — over a decade in all.
Disappointed with A FEAST FOR CROWS, I eagerly awaited A DANCE WITH DRAGONS. It was a disappointment akin to Star Wars prequels for this troper, and for similar reasons: The author's unwillingness to cut. Virtually nothing happens in book 5 except for major cliffhangers at the very end for all your major characters.
Martin could get away meandering early in the series, because he was still world-building. We don't need it anymore; we know who's who, and what things are. We're just looking for the resolution to plots introduced as early as...oh, the prologue of book one.
Dragging them out it one way to guarantee future sales and more seasons on HBO. But the series has degenerated into ongoing soap opera. The last event worthy of mention (were I telling the tale in oral tradition) happened in book 3.