You definitely saved yourself, the show took out so much stuff, which was kind of inevitable, but the amount they took out in order to slap in some trash was a bit aggravating. Spoilers below.
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And even knowing how seemingly pointless some of the stuff would turn out, it’s odd they kept any of the Dorn stuff in in the later seasons. I get that Pedro Pascal was awesome, but the Dorn stuff in the show was even more pointless than it was in the books.
Biggest sin I think though was leaving out Lady Stoneheart. In GRRM’s mind, I suspect Arya’s story is so deeply intertwined with her’s that to leave her out just basically knee-capped Arya’s revenge-fueled character arc, she’s headed for a confrontation with LS, to see a sort of mirror-image of herself. In the show she was given a somewhat unearned “consolation prize” that just seemed stupid.