I will now list all of the things I dislike about Jacqui, in order from my biggest complains to nitpicky ones. I'm very sure, that most people, who dislike Jacqui will agree with quite a few of these points. Everyone else will see that none of these -in my opinion very valid complaints- have anything to do with Jacquis skin color or her gender.
1. I'm big into variety, when it comes to different playstyles in fighting games. Jacqui in my opinion doesn't bring that variety, because she is not only a regular human from the Special Forces... but she is also heavily modelled after her dad, who is another character. I like to compare her to She-Hulk in UMVC3. She-Hulk has the exact same power set as Hulk, yet she plays differently. But visually speaking, there is still not enough variation for me to really stand behind a character like She-Hulk. Or X-23. Or Jacqui Briggs.
Instead of those characters, I would like to have characters, who have an entirely different playstyle from the rest of the cast. Characters, who aren't similar to anyone and just do their own thing. She-Hulk smashes things in a different way than Hulk does. X-23 slashes things in a different way than Wolverine does. And Jacqui Briggs shoots guns and punches things slightly differently than her dad Jax.
I dislike Cassie for the same reason. Cassie doesn't really add anything to MK gameplay-wise. She is her dads and moms daughter. She shoots guns and copies a couple of their moves. Sure, she has a sassy personality, but that really doesn't up for the lack of her uninspired gameplay.
And I'm perfectly aware of the fact, that you might think differently about all of that. Maybe a couple of different special moves are enough for you to view a character as their own thing. But for me personally that's not the case. I want stronger visual and playstyle-related distinctions.
2. A playable character like Jacqui Briggs requires NRS to put artists on her to conceptualize her as a character. Then they need stunt-women to motion capture her moves. Then they need 3D artists to design her. Then they need balance testers, a voice actress, various visual items and so on. All of that costs time and money. That time and money are being put into her instead into a Sindel, or a Rain, or a Smoke or whomever more people would prefer to see. (Again, at the same character, who would in most cases come along with a unique playstyle.)
3. Jacquis role in the story is absolutely horrible. I've said it many times. Jacquis main purpose is to be Cassies best friend, Takedas love interest and the reason why Jax joins the fight. With that backstory she is the weakest of the Kombat Kids by default. All the other ones had a stronger backstory and more character development. Even Kung Jin, who isn't really that related to other major characters. But he at least has some stuff going for him and he was pretty much the only Green Arrow in modern MK, so he also had a distinctive playstyle. Jacqui did not. She was just there.
4. Jacquis design was absolutely, positively horrible in MKX. She legit looked as bland as generic as you would imagine regular canon fodder SF members to look like. That is unacceptable in a world, where you have insanely amazing character designs such as Scorpion, Sub-Zero, Smoke, Raiden, Mileena and many others.
5. Last but not least is the mere fact, that she is such an underwhelming >>> NEW <<< character. When you have a universe with such a large number of crazy cool characters, all of your new characters really need to kick the ball out of the park with her playstyle, their design, their personalities and so on. They have some big ass shoes to fill... Especially if characters such as Smoke, Rain and Mileena get benched in the process.
But Jacqui didn't have anything amazing going for her. She was too bland and too generic to compete with fan favorites, who are fan favorites for a reason. As I said before, 10 years down the road, Jacqui will be the Kobra of the modern era. No one will care about her. That is, if she remains as lackluster as she is right now.
And it's really, really important to note, that when I personally trash talk Jacqui, that I don't trash talk her as a single character. I trash talk her as a character, who has to go up against much, much, much cooler MK characters. And she is a character, who can't compete with these characters in the slightest. So the question becomes... What is the point of Jacqui?