Josh Trank, director of Fantastic Four (2015), revealed he wanted to cast a black actress as Sue Storm but received pushback; the role ultimately went to Kate Mara. Leading up to the start of production on Fantastic Four, Trank selected a whole new cast of characters to play Marvel's First Family as 20th Century Fox looked to reboot the franchise following Fantastic Four and Fantastic Four: Rise of the Silver Surfer in 2005 and 2007, respectively. Miles Teller was cast as Reed Richards aka Mr. Fantastic, Jamie Bell as Ben Grimm aka The Thing, Mara as Sue Storm aka Invisible Woman, and Michael B. Jordan as Johnny Storm aka Human Torch.
Some Marvel fans reacted negatively to Jordan being cast as Johnny Storm, a character who's typically been drawn as white in the comics, and who was played by white actor Chris Evans in the 2000s movies. The Fantastic Four casting backlash was so bad that, at one point, Trank bought a gun because he was so paranoid during the film's production. Trank's movie kept Johnny and Sue as siblings, but established the latter as the adoptive daughter of Franklin Storm (Reg E. Cathey), rather than his biological daughter. However, Trank originally envisioned the whole Storm family as being played by black actors.
Speaking to Geeks of Color, Trank was asked if he ever considered casting a black actress as Sue Storm. Trank confirmed he had wanted to have Sue be black alongside the rest of the Storm family, but received pushback from the studio. He said:
There [were] a lot of controversial conversations that were had behind the scenes on that. I was mostly interested in a black Sue Storm and a black Johnny Storm and a black Franklin Storm. But I also, when you're dealing with a studio on a massive movie like that, everybody wants to keep an open mind to who the big stars are going be. Like, 'Well maybe it will be Margot Robbie,’ or something like that. But when it came down to it, I found a lot of pretty heavy pushback on casting a black woman in that role.
Considering both Johnny and Franklin Storm are black in Fantastic Four, it certainly would've made more sense to cast a black actress as Sue rather than hamfist the backstory about Sue being adopted. It's also unclear whether Fox believed Mara to be a big-name draw when she was cast in Fantastic Four. Although she's no doubt an established and talented actress, she's arguably not a movie star akin to someone like Margot Robbie now - or even Robbie when she was cast as Harley Quinn in Suicide Squad. So if they weren't going to cast a major star as Sue, it would have been better to cast a black actress. For his part, Trank regrets not fighting for what he believed in when it came to casting the role:
When I look back on that, I should’ve just walked when that sort of realization hit me and I feel embarrassed about that, that I didn't, just out of principle, because those aren't the values that I stand for in my own life and those weren't the values then - or ever - for me. Because I'm somebody who always talks about standing up for what I believe in, even if it means burning my career up, and I feel bad that I didn't take it to the mat with that issue. I feel like I failed in that regard, but that was a weird, unfortunate situation, I don't know how else to put it.
Considering how much controversy was created by racist fans who took issue with Jordan's casting, it's no doubt there would have been even more if Trank had also cast a black actress as Sue in Fantastic Four. Still, it would've made more sense than having a white actress play Sue and force the movie to explain she was adopted by the Storms. It's unclear why the studio didn't want Trank to cast a black actress in the role, but he implied it was because there were no up-and-coming black stars on the same level as Robbie or Mara (which is doubtful, to say the least). What may be more likely, given the systemic racism that pervades Hollywood, is the studio balked at having two of the four members of the superhero team be black. However, unless Trank or someone else involved in the movie confirms as much, that's just speculation. For now, Fantastic Four fans can look forward to the team being rebooted again for the Marvel Cinematic Universe now that the character rights have moved to Marvel Studios.
Source: Geeks of Color