D&D saying that one of their favorite plots from the books is the Boltons in Winterfell is a massive sign of their sexism. Now, for anyone one else, I'd probably not care, in fact, I'd agree it's a very interesting part. However, when it comes to the showrunners who needlessly wrote in excessive rape and violence against women, I see it as a red flag. That's compounded by the way they wrote it.
From the beginning of the show, D&D sabotaged the storyline by removing Jeyne Poole. Keep in mind, ADWD was released in 2008, while GOT premiered in 2011, meaning there was no possible way for D&D to not know everything necessary to bring about that specific plot. Add to that the fact that GRRM was heavily involved in season one, them blatantly ignoring Jeyne makes even less sense if they truly cared about adapting it properly.
Knowing this, that D&D themselves sabotaged their own story, the way it was handled makes a bit more sense, though not nearly enough. Without Jeyne there to play the part of fake Arya, a new bride for Ramsay was needed. Sansa was D&D's favorite character, they were unsatisfied with the story GRRM had written for her, they wanted more screen time and plot relevance for her. It seemed like making Sansa take Jeyne's place was a good solution to both these issues.
Except it wasn't. Littlefinger sending Sansa out of the Vale to marry Ramsay makes no sense. Not only is Sansa the object of Littlefinger's obsession, a replacement for Catelyn in his mind, she also was important to Littlefinger getting the Vale on his side (in the show). She was charming the lords and knights, balancing their intense dislike for him with their desire to help/protect her. Not to mention she was his only alibi to save him from accusations of Lysa's murder. Sending her away from the Vale harms Littlefinger's plans. She also would definitely not be "protected" from Cersei; after all the Boltons were loyal to the Lannisters and hated the Starks, what's to stop them from killing Sansa or handing her over once the Northern lords are more settled?
Speaking of the Northern lords, D&D removed the Northern Conspiracy. Throughout the book plot, the Northern lords are plotting to save Arya and depose the Boltons (in a nutshell, it's actually much more complex, but I'm not going into that rn). It's an excellent expression of how the Northerners loved the Starks and hate the Boltons. In the show, the lords are a bit disgruntled, sure, but they have no interest in deposing the Boltons and saving Sansa.
Another major part of the storyline minimized by the show is Theon/Reek. Theon's struggle with identity is a major part of his character throughout the series, and ADWD is no different. He's been stripped entirely of his identity by Ramsay's torture and Theon's own choices. Part of his arc in this book is discovering himself apart from the Starks and the Greyjoys.
That's definitely not what the show did. As I said earlier, Sansa is D&D's favorite character, so naturally she became the center focus of this arc, while Theon was pushed aside. He's essentially reduced to the method of Sansa's escape and goes on track to return to his pre-season one perception of himself: a Stark. This is a massive disservice to his character, Theon isn't a Stark; his life with them is important to his storyline and will definitely inform what he becomes, but it's not the true culmination of his arc. Basically, Theon was turned into a side character in his own story. It's through his pov we see this story, he's the character most tied to Ramsay. Obviously Jeyne is important and a main character in her own right for this arc, but she is not the central character we see the story through. So why is Sansa? She has no stake in this story, Jeyne is forced there after being sex trafficked and Theon is a captive.
So what does this leave for the show version of the plot? There's no conspiracy, Theon's pushed to the side, and politics and overall story are sacrificed. Well that leaves torture and violence against Ramsay's bride. Without the many moving parts of that storyline, it's just a story of a woman being abused horribly by her husband and eventually escaping. However, the escape isn't even the main aspect of the story focused on, that's always the abuse. It's also purely Sansa's abuse, not Theon's or the many people tortured and murdered by Ramsay, Sansa is the sole focus.
So basically, D&D took a plotline that's filled with the inner workings of Northern politics and the complexities of battling identity loss and reduced it to another excuse to show a woman be raped and abused on screen. The desire to turn this stroy into another way to make Sansa suffer is disturbing, and to make matters worse she fucking thanks Ramsay later on?? This whole storyline in the show is disgusting and yet another sign of how sexist D&D are.
What's mindboggling is that D&D loved Sansa but also put her in a situation where she's tortured and abused. You know, almost like they enjoy their favourite female characters to be so victimized...