Mom asked a question about this outfit I want to wear, Why can't I wear it? I'm 11-years old. My mom is 17.

By wearing this outfit, the world will judge you based on the traits of your body, not your inner being.

Explanation:

Know that every bit of our universe is perfection, even you. So, it would be meaningless to try to make yourself good-looking through these outfits for it will only make others gaze at you in a very rude perspective. Therefore, it is a good decision to wear normal outfit, as it will let others know you through the true beauty of your inner qualities, not your body features.

I don't see a problem with wearing that

pitch- the definition of pitch is as follows:

"the quality of a sound governed by the rate of vibrations producing it; the degree of highness or lowness of a tone."