Gotta love the usage of sweeping generalizations in order to promote negativity, especially in a thread whose sole purpose was so positive
Anyway...
I could go on and on about how much I like the character, but I'll keep it succinct and just add that, the way I see it, Sonya has that "Batman" factor going on: a regular human in a world of fantastical "metas", who not only manages to keep up, but also surpasses many of them. In my opinion, that's a handful of times more appealing and interesting than mere aesthetics, or "cool power, bro!" Outwardly, this is just some blond chick standing next to demons and monsters, and yet, look at the story of MK so far (especially recent games), and she's kicking ass left and right, and leading the defenses of the planet. I just love the ever-living-crap out of that aspect of her character: looks like she should be an underdog, but ends up proving consistently to be a top contender. That's just dope as all hell.
Additionally, I'm one of those people who welcomes and embraces the drama in the story that is not reliant on fighting and violence. I don't like one-dimensional things, and I don't like superficiality--I like it when a story has many moving parts of varying degrees and importance to the over-arching plot, and especially so, I enjoy characters who are human, and relatable. I understand that it's MK--it's a fighting game, and it must rely on fighting. But why not have real characters in its plot? I love the comic interactions between Sonya and Johnny in MK9, the levity it added to everything else, and how it developed into an actual rocky relationship, where they're saving the world together one moment, and nurturing a broken family the next. They came out the other side as much more complex, mature individuals, and through this, helped elevate the tone of the story in much the same way. I know and understand that Scorpion's the "mascot", and easily recognizable across genres, but objectively, he hasn't added anything to MK to the point that Sonya and Johnny have, especially in recent games, and so I will respect these two infinitely more. And I'd wager that NRS agrees with me, going by MK9 and MKX: they've been using Scorpion as he should be used, as a marketable character, and utilizing the likes of Sonya to broaden the story, aid in its progression, and elevate it.
As for the apparent "hate"--I don't see it; at least not to an extent that's more egregious than any other. Every character gets their share of hate for various reasons, and when I've seen Sonya hate in forums, it's nearly always been from those who want to target her for having "stolen the spot" of their favorite character whom they haven't seen in a game in years. And that's just shaky "hate" at best, baseless whining at worst; as if her absence in the game would have automatically meant that their favorite would suddenly show up. That's not how that process works, guys and gals. No Sonya would have just meant no Sonya, it wouldn't have meant automatic Fujin or Rain or Havik or whomever else. It's also worth pointing out that negative talk around Sonya seems to be reserved for online forums. I've read more than a few articles about MK11 that have referred to her as "fan-favorite", especially back during the Rhonda reveal trailer, and I was heartened by the myriad positive comments on YouTube videos and the like, and by the amount of people freaking out about her potential "death" after the IGN Cassie/Raiden intro. So the consensus, it seems, is that when it comes to the general audience, she's very well-liked, and a staple of MK--and luckily, NRS is perceptive of this, as they've been doing a great job with her for years, story-wise and gameplay-wise. And I simply cannot wait to get my hands on her very soon (come ooooon, beta).