I think the issue for the OP is that Disney doesnt have a dress code up to his/her/their standards, and therefore should address this with Disney first. If you want Disney to ask people to cover up, they first need to put it in their T&Cs.
And to your question: yes, people who put on clothes usually think they look good in those clothes.
Especially when you see 14/15 year old girls, they are trying to find their style, trying to fit in, and that is not always in the most comfortable outfit.
For women in heels, for some it is about being seen, instagram and all that jazz. It is not about the rides and shows and characters, they want to show how they look on instagram with a nice background. Your legs and booty usually looks better in heels.