If Lisbeth was the perfect heroine, we would have seen more like her in fiction.
I understood her thinness as the result of drugs & smoking, rather than a model-like ideal of femininity. (I have known quite a few people like that. you would be surprised how thin you get despite junkfood when you crank up your metabolism and dance all weekend, 48 hours straight with no time off for sleep) Also, I didn't think she had superhuman strength, but was vicious and violent because (1) she learned to defend herself and (2) she had little empathy and social inhibition.
The last two are obviously related to an ASD condition, and I would think, so is her brilliance in fact collection & pattern recognition (research). She reminds me of a corporate lawyer I used to know - completely inept in anything remotely social, even conversation, but would put together complex legal structures that nobody would even understand.
Meanwhile, Blomkvist got targeted by a powerful man who then discredited him because he wrote investigated and wrote a damning article about the guy. It wasn't an improbable coincidence, imho.
Anyway, to each their own taste in books, of course. Agatha Christie it certainly ain't 