I don't agree with you re: Sansa. That's just a matter of taste, and yeah, she isn't a fan favorite, but I know plenty of people who love her. I like both girls, honestly, but I'm wont to defend Sansa.

I do find Sansa interesting. First and foremost because between her and Arya, she is the most realistically portrayed for women in that world. GRRM writes some great women, and the women of his world mirror those of ours. (As an aside--this is why I believe Cersei gets so much hate and Jaime doesn't. She's a woman and the only power has at her disposal is sexual, so she's seen as a slut when really it's just a bargaining tool. Jaime, meanwhile, is praised for his redemption arc... what redemption arc, I ask?)
ANYway, Sansa is like most other ladies of Westeros who aim for/aspire to be feminine. Arya is the exception the to rule, the special snowflake who doesn't want to adhere to the norm... and I think it's interesting to read about the lady who doesn't want to be different, for a change. She doesn't scheme like Cersei or learn to fight like Arya. She's one of your girls that just wants what most other girls her age want, and that's really relatable. What I'm saying is: Not everyone wants to be or
can be special snowflake. And I think she gets flak for that where Arya gets praise. Moreover, Arya can be strong and feminine (I never said she wasn't), but when I say she's praised for her strength, it's the traditional strength she's praised for. She may preserve her femininity, but people are still cheering for her because she adheres to traditional strength. That's what I'm trying to say. She proves that girls can kick ass, yeah, and there's no question about it, but the real issue is that that seems to be the reason why people like her. (And also why people hate Sansa and Cersei.) And by "people", I mean the majority of fandom, just to be clear.