LF's brains? She hasn't shown any cunning aside from pulling of a sob story after Lysa's death. That was nothing really. An easy circumstance to exploit.
The point is that's how LF characterized her, as the daughter of Cat and himself. Sansa didn't protest that by reminding the dude that Ned was her dad. A Stark would assert their Stark blood. Jon was on the precipice of forgoing his Watch vows in exchange for the name he always wanted. Dude wrestled with that shit. Jon knows the name of Stark is worth risking life and limb, is something to be proud of and assert. Jon is such a great fucking Stark that he declined the Stark name to rock the Stark spirit. Sansa just lets LF's slight slide. She even learns her family history from LF in the crypt... Arya would know about Lyanna on her own. Shit, Arya *is* Lyanna come again. Arya *can't* even lie her way out of being a Stark. In this very episode, dude sees right through her lie to her undeniable Stark self. She keeps Needle! Sansa has no such connection to Stark.
If your claim is she's not only missing the Stark steel but also the Baelish wit then yes I would agree with you. She's a useless flowerpot idiot.
Everyone wants her to blast Ramsay because they love Stark and they hate Ramsay but it's weird to expect Sansa to do that herself since she's not a Stark in any way that matters. If the North rose in support of her it'd be in support of her name, not in support of her personal worth. The people who marched south with Robb to avenge Ned would be flabbergasted by this Southron doofus sitting under a wolf banner.
We want Sansa's North story to be about her finding her Stark roots. But so far the only W she's put up since coming to Winterfell was her LF-esque slam on Myranda (which didn't even accomplish anything for her...).
Save some dramatic shift in her arc, she's currently developing into Littlefinger's heir. Which means her play will be to seduce Ramsay into complacency and then murder him ignobly and then only because doing so advances her interest. Sansa isn't on a path to strike down Bolton in the name of Justice, she'll do it in the name of Scheming. We'll all be psyched when it happens because Fuck Ramsay and Long Live The Stark in Winterfell, but we'll be wrong to feel that way. If Sansa only manages to fly the Stark banner using LF's methods, it'll be the End of the Starks as we know them, as we want them to be.