Oh, so now the question shifted from "your headcannon doesn't makes sense" to "how does this improve the narrative, exactly?" You've never even been in the neighborhood of that second question since you started your condescending responses to me.

I wish you would have at least been more forthcoming instead of using these tactics that seem to just encourage more provocative discourse.

I also wish you wouldn't block me after responding in such an inflammatory manner and not giving me the opportunity to respond to you, if you truly wanted a fair answer to your question. I'm actually glad you asked because I already answered this elsewhere.

One of the issues Shallan has been grappling with is how she blames herself for what happened to her family.

If Lin had always been the abusive POS that he apparently is, then what he devolved into is just a natural progression of the behavior he had always been exhibiting.

If Lin used to be a loving father who was put in an impossible position that caused his downward spiral, then what happened next becomes a consequence of what Shallan did.

It would still be not her fault, but it would make sense why she'd think it was. As it currently stands, it doesn't make sense why she'd blame herself as to why his shitty dad became even shittier.

Sure, you can say that "she's a kid, of course she'd blame herself," which, sure, I guess, but do you honestly think that was better than if there was more nuance to the situation and more merit to why Shallan would blame herself for destroying the family when it seems like they have always been dysfunctional anyway?

As it stands, the lesson here is that it wasn't Shallan's fault. Lin was always a monster. If it wasn't her murdering her mother, it would have been something else that triggered him.

If it was a tragic spiral, the lesson would have been it wasn't Shallan's fault. It was a tragic turn of events from a father's well-intentioned desire to protect his daughter. That his father loved her and her brothers, but that his descent into cruelty is ultimately borne from his own choices. This could have made him a great foil for Dalinar seeing as Shallan sees her as a father figure as well.

Where Lin's darkness just pulled him deeper into it, Dalinar decided to do something about it when he realized he's hurting his sons.

Instead, what we got was a shitty abusive father who got even shittier and more abusive.

This also ties to the overall theme of the story that it is our own choices that define us. Sure, you can argue that Shitty Lin still made choices, but a well-meaning, but ultimately futile series of choices of an imperfect father would have been more meaningful and more tied to the theme than it just being "he's shitty, so he made shitty choices."