I do think GRRM is struggling to tease the rest of the story out, but I don't think that was the problem at all with GOT. The key plot points were all basically

I do think GRRM is struggling to tease the rest of the story out, but I don't think that was the problem at all with GOT. The key plot points were all basically fine. It just all felt so rushed and totally unconvincing. Daenerys going mad and Bran ending up on the throne are reasonable enough directions to take the plot, but the show completely failed to develop either of those things, so when they did happen it just felt forced and not believable. They also did a bunch of other annoying/bad things that deviated from the early seasons (bringing along a bunch of nameless characters on adventures to just to kill them, wardrobe and makeup went in a frankly absurd direction for no obvious reason, emphasis shifted to "wow" moments in episodes instead of paced out plot, just dropped a bunch of story lines that were interesting, etc).