I think the basic problem with the show is not that they've gone out on the limb and tried too many new things, but that they've kept the plot absolutely still for 2 seasons.
What worked in the first 4 seasons was the idea that the Lannisters were winning, and the Starks were always in a state of remembering and avenging.
Once they abandoned that dynamic, the plot shifted to smaller stories, but D and D held fast to the dynamic of some other house winning, and the Starks always in a state of remembering and avenging.
This is why Ramsay, despite having the same role in future books and being played by a fantastic actor, is grating.
George R.R. Martin wrote a character named Joffrey who was unbearably smug and vicious, and undeservedly won a war. Then he killed him. D and D gave him a more handsome face and a 6 pack.