I guess my issue lies with the artistic presentation which, in the last two seasons, is closer to Marvel than to Martin's original work. Visually it's stunning but the tone of the series has definitely changed a lot. I'm not one of the people who will refer to D & D as "dumb and dumber" since Benioff has written two books i thoroughly enjoyed (one of them, the 25th Hour, became an excellent movie too) but i can't help but feel that they really missed a trick here.
I didn't expect the show to end with Daenerys becoming a benevolent ruler and restoring order in Westeros. Dany's character development from a "breaker of chains" who would break the wheel (her own words) into the Mad Queen is a development that could definitely make sense on the show. In fact, it is a development that seems much closer to Martin's worldview than to any LotR-like "happy ending". A worldview where the darkness that resides in the human soul and the absurdity of violence upon which each phase of human civilization has been built steadily lead a civilization to ash.
Some of my favourite scenes in the show where the ones with Tyrion and Jorah travelling through the ruins of Valyria, a civilization that once stood great and proud but now lies forgotten in debris with death being the only thing that has survived. That was back when the writers still had the time and the will to portray the show's worldview on screen and not on the next week's "previously on GoT". So, you're right that Dany will become a psycho, Jamie will be a loser, Jon will be an incompetent sap. And in the background, Stannis will always be burning Shireen alive and all the great buildings in KL will be burnt to the ground.
After the original material ran out, the narration became more minimalistic, more "1+1=2". This has hurt the show in the same manner in which the writing has hurt the second season of Westworld. The characters lose their depth, their "three-dimensional" status, and become just symbols that represent just one thing. The problem with GoT is that its characters were never like that. Despite Daenerys becoming the Mad Queen always being in the cards, her transformation seems plausible because it is in tune with the heart and soul of the story overall but it was completely out of sync with everything we've been watching up until the main characters started talking about it in the last two episodes. You could see this particular outcome but it was handled with very little grace. This should have been an episode that would make TV history. And not just for its special effects.
Sorry about the rant, just my two cents on the matter.