Translating comic characters to the big screen is a massive undertaking. Trying to retain the silly yet essential elements that define iconic superheroes is an arduous process that requires copious amounts of creativity and studious attention to detail. If you make a Superman adaptation without Clark Kent's glasses concealing his alter ego, the film may be a bit more realistic, but it would compromise a core component of the character.
Outside of tropes and characterization, the same logic applies to superhero costumes. However, it's practically impossible to squeeze real human beings into comic-accurate outfits, as they're typically thinner than a layer of body paint. Some film studios can find a decent middle ground that carefully retains the character's comic book aesthetic without turning the costume into an overworked mess. And then there's the Marvel cinematic universe that hasn't met a costume they can't make needlessly complicated.
In the video linked above from Browntable's YouTube channel, you can check out a brilliant and brief essay explaining why Marvel's movie costumes seem so busy.
