It's not provable. Maybe they think all superhero costumes look dumb. Personal preferencws cannot be disproven. Just cause you like them doesn't make it a false statement or provable. Your opinion is just that, an opinion. Just cause superhero movies make money, is the guy who directed Birdman wrong for saying they're bad? It's the same thing. Your argument is just based on being a fanboy who doesn't like people making fun of what they like. But it doesn't make your argument that you are presenting valid. If you hate olives, no argument in the world about how great olives are will change the fact that you don't like them.
The showrunner doesn't have to like superhero costumes or think they are cool anymore than you have to like the Netflix shows for shying away from them.