Here's the thing about casting actors for live-action depictions of beloved characters in our modern age: It's almost impossible for filmmakers to avoid criticisms from the characters' most ardent fans.
On NPR, Glen Weldon pointed out that Zack Snyder is going through this process right now with his casting of Gal Gadot as Wonder Woman. I've long maintained that the most obvious person to cast as Wonder Woman is Beyonce, but I also say that as someone who doesn't have much emotional stake in the matter, and who mainly wants to see Beyonce in the role because I suspect it would create all sorts of cognitive dissonance for fans who think of Wonder Woman as Linda Carter, not the canonical comic book character.
I'm also the kind of person who has suggested that Wonder Woman is the perfect property to use in a television show about a group of friends, one in which the super heroine is merely one of the ensemble, famous and powerful but at the same time just one of the men and women in a tight-knit group of friends who are all fleshed-out characters, themselves. And that's because the Wonder Woman canon has been malleable from the start; she has multiple canonical origins, and so it's not really heretical to re-imagine her as someone who has a close group of friends with whom she shares her secret identity*.
*So help me, don't call it a "Millenial show"...
But how Wonder Woman looks is not up for debate among the entitled masses. Weldon has it right that, ultimately, the character's physicality doesn't matter as much as her gravitas, but that how she looks is what fans can see and complain about right now, so they will. Alyssa Rosenberg gave us, to my mind, the classic description of this phenomenon in examining why so many people have written online that they will be disappointed unless Matt Bomer and Alexis Bleidel are cast in a Fifty Shades of Grey movie. Bomer and Bleidel's physical appearances roughly match the appearances as described in the book... and nothing else matters. Not their willingness to take on those roles, and not the filmmakers' opinions of those actors' talents.
But while Fifty Shades has yet to play out completely, Snyder can also turn to the controversy surrounding Jennifer Lawrence's casting as Katniss Everdeen in the Hunger Games movies for evidence that if the actor's appearance inspires only some gnashing of teeth, the movie is well-made, and the acting is satisfactory, that will be good enough for the non-zealous. Because, again, before the movie comes out, all we have to go on is what Gadot looks like, and so that's what the nitpickers will nitpick.