Well i mean they did throw away alot of what was provided to them. To quote the man himself be said be provided them with enough material for 13 seasons
Bullet points and outlines are not sotorylines. They made 4 and a half seasons out of 4-5 books. I don't think he wrote them 5 additional secret books for those other 5 seasons.
Danny becomes mad doesn't tell the story of her slow descent to madness. Bran becomes King doesn't tell you how the weird tree kid gets the most powerful position of the kingdom. Ideas are not material. They were making an adaptation not trying to write a story. The actual writer stopped writing.
HBO pushed for atleast 10 seasons but D&D refused to go higher than 7,5 seasons because they felt they needed no more than that to finish it strong.
The white walkers had been comng for 5-6 seasons. Arya spend the whole 5 season spinning her wheels. Danny kept delaying her going to Westeros. Let's not forget that the showing has been spinning wheels for a couple of seasons now. They actual show didn't actually show it some roadmap to make another 4-5 seasons. They had bullets points that went in contrast to where they were with no ideas how this happen.
They could either do remaining bullet points with no idea how George was going to do them(because he hasn't written them yet) or do their own things. They chose to stay an adaptation and do the first. Poorly but they did.
And the only reason they could get away with that retroacticely recognized to be bullshit pitch was because the runaway success of GoT was mistakenly assumed to be due to some sort of perceived competence on the part of D&D,
They did a decent job at making a good show when they had actual books to get material from. The Hobbits movies not being great does not suddenly mean suddenly mean Lord of Rings movies were not great achievements. They were good at adaptating.
when what was needed was for people with input to say no you don't have the means to wrap this up this soon, this needs fleshing out, this is to abrupt. Essentially what they needed were producers, editors, script doctors and other collegues with the balls to say that the emperor is naked.
Again with the emperor thing and that supposed smugness. They were trying to adapt not write. Their actual writer stopped writing. Than they spinned some wheels before deciding to cut the cord rather than do some kind of agonizing bastardization for the next 2-3 seasons or simply deviate for GRRM.
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Again I'm not some secret fan of their work. I didn't even bother watching the finale. I didn't want to be part of the viewership they would brag about and that BS last episode annoyed me for the whole week. So I happen to think they did a poor job. But I also think that poor job comes partly from no longer adapting material rather than pure malice.