Recently, Cara Delevingne was interviewed by Empire Magazine. She plays the character Enchantress in the upcoming Warner Bros. DC Comics movie "Suicide Squad." In the interview, she was quoted as saying "Generally though, superhero movies are totally sexist." I'm not going to address whether or not superhero movies are sexist. It's her reasoning that I will address. During the interview with Empire, she continues to say "Female superheroes are normally naked or in bikinis. No one would be able to fight like that. Wonder Woman, how the hell does she fight? She would be dead in a minute."
For the most part, superheroes (men or women) are not naked or scantily clad. Other than Jon and Suzie from Sex Criminals, I can't think of any naked superheroes. But for those who are scantily clad, that doesn't affect their crimefighting. When Bruce Banner turns into the Incredible Hulk, he is wearing nothing but shorts. It wouldn't make him a better superhero if he was wearing a shirt as well. Or boots, gloves, etc. He would still be as strong and agile. In fact, if he wore more clothing like pants (instead of shorts) or a shirt, he probably wouldn't be as agile.
Look at Clark Kent. As Superman, he wears a simple skintight suit with a cape. Does the suit make him Superman? No, it doesn't. He wears the suit so others won't realize that he's also Clark Kent. Superman sometimes even fights crime wearing a t-shirt and jeans with a cape. Without his suit, he can still fly, lift heavy objects, use heat vision, have bullets deflect off him, among other things. His suit doesn't give him super strength, agility, and stamina. If anything, he might be more agile without the cape.
There's also the theory that Clark Kent is his alter ego and Kal-El is his true identity (which it actually is). But superheroes like Batman and Spider-Man wear their suits to cover up who they really are, Bruce Wayne and Peter Parker. But Clark Kent wears human clothing to cover up who he really is, Kal-El a.k.a. Superman. With a suit, Batman is still Bruce Wayne. He will always be Bruce Wayne (or Dick Grayson or Jim Gordon or whoever is wearing the suit). Batman is not always Batman. But Kal-El is always Superman. Sometimes he's Clark Kent, but he's always Superman.
Or even Wonder Woman, who Delevingne mentions. For most of her history, Wonder Woman has shown more skin while fighting crime than most superheroes. But she does wear a suit that covers up everything except her hands, neck, and head (she also wears a tiara). Her suit is for convenience purposes, like carrying her sword and lasso. With this full body suit, you see more skin from superheroes like Martian Manhunter, The Incredible Hulk, Wolverine, Supergirl, Robin, and sometimes Batman. But regardless of what she wears, Wonder Woman can still fly and possess her superpowers.
There's even Dr. Manhattan from Watchmen. He's almost always completely naked and still has his superpowers. Unless you're someone like Bruce Wayne or Tony Stark, you don't need a suit to be a superhero. If anything, most superheroes could benefit from wearing less. Not wearing a cape would increase agility and speed. People would be less likely to recognize you if you were nude. Imagine going through a Where's Waldo? book and everyone was naked. It would take a lot longer to find him. His glasses and face would be the only give away.
I would like to answer Delevingne's rhetorical question "Wonder Woman, how the hell does she fight?" She fights by simply being who she is. It doesn't matter what she wears. She will always have her powers, strength, agility, and stamina.
