First, there is nothing anywhere in the FF mythos that specifies what race any of the original team members are, other than what Stan Goldberg did with the coloring back in 1961 and everyone has copied since. And while decades of coloring the characters one particular way sounds like a significant precedent, it isn't. It's simply a superficial aesthetic, just like the specific design of their costumes or the particular slang any of the characters use. What might be relevant to whether the Torch is played a Black man would be if the character had some history or background that was uniquely tied to the experience of being raised as a particular race. For example, if Franklin Storm (the Torch's father) were a member of the Klu Klux Klan and was shown to have participated in violently racist behavior, which then impacted the Torch's own views on race... that would be a valid reason to keep the character white.
But there is nothing -- not one single thing -- in the Human Torch's history that speaks to his own race in any capacity. In fact, he has a history of being very open and accepting about other races. One of his earliest and longest friends was Native American Wyatt Wingfoot; his first serious girlfriend was the Inhuman Crystal*; he even married the Skrull Lyja. In fact, there's only one instance where Johnny is shown to have anything resembling racist tendencies when he throws "mutie" out as an epithet and soon finds himself regretting it. So, at most, you could claim that he should never be shown to be a mutant. But beyond that, there's bupkis about his race.
I caught a snippet of the Nerdist's initial analysis/reaction to the trailer, and they referred to Kate Mara's Invisible Woman character as Johnny's adopted sister. Presumably because we see Franklin Storm played by Reg E. Cathey. Unless it's expressly stated somewhere in the movie that she's adopted (and while I admit that I haven't kept up with every nugget of info on this movie, I haven't seen anything official that's stated as much) I have to say that I think that's very small-minded thinking. Yes, Mara has a very much lighter complexition than Jordan and Cathey. And her hair displays none of the traditionally short, tight curls that are generally seen with Black women's hair. But given that Sue's mother is not in the film at all, who's to say that she isn't white? It's entirely plausible that Sue and Johnny are indeed genetically related in this film and just inherted different traits from different parents. That's how biology works. Mixed race children -- or any children, frankly -- won't necessarily look just like one parent. Maybe Josh Trank said somewhere that Sue was adopted, but if not, then it strikes me as kind of offensive to assume that.
Here's the thing: there's nothing in the trailer to get upset over. Because there's nothing in the trailer! If you don't already know the characters and the story, or have some vested interest in the actors, there is nothing in this trailer to tell you anything worthwhile about the movie. Nothing about the plot, nothing about the characters or their relationships to one another. Even the narration is incredibly vague. Frankly, I think it does a phenomenally bad job of being a trailer. It barely even conveys any tone since we get so little dialogue. The only reason fans are able to tease out any information at all is because they've already done a ton of research going into it, and this provides a small handful of new visuals.
I don't recall seeing any of these actors in anything before. I don't know their skill levels in that regard. I've never seen anything Josh Trank has done before. If they're not talented, or have done poor jobs in the past, that's something to legitimately criticize. If you were expecting a trailer with something of substance, that's something to legitimately criticize. But complaining because a character who was played by a very Aryan-looking guy a few years ago is now played by a POC, when race is absolutely not an issue anywhere in the character's history? Do us all a favor: go see the Goosebumps movie that opens the same weekend and shut the hell up.