A DANCE WITH DRAGONS has certain thematic ideas - the tragedy of failure and unrealised ideals (with Dany and Jon, who both have great intentions that blow up spectacularly in their faces), and an attempt at redemption that tries to avoid cliche (with Theon, who has done things most would take as irredeemable). Arguably the former thematic point fails to take, because Dany's story ends too early (the Battle of Meereen, its culmination, has been pushed back to the following volume) and Jon's features too many filler chapters, but Theon has certainly proven a popular storyline.

In addition to that, we have a massive geopolitical shift that unfolds over just a couple of chapters (the Golden Company's invasion of Westeros), major backstory revelations (our understanding of the Stark history needs to be majorly rewritten after learning that Brandon was a Grade-A arsehole) and the best concluding chapter of the entire series (for me, anyway).

The lack of resolution to several key storylines is a major structural issue, however, as is how the POV are assembled. Perhaps making a shorter novel that was 'only' the flipside of AFFC and then a unified novel featuring all the characters and went a lot further down the timeline would have been a better choice, although the flipside book would have lacked any kind of narrative cohesion.

On the other hand, CROSSROADS OF TWILIGHT is almost entirely skippable filler (any Internet summary does the story justice). A few interesting character moments aside (mostly for Tuon), Jordan failed to move on the storyline, character arcs or thematic ideas of the series forwards in any meaningful manner, as DomA outlines.