There is a qualitative difference here which you are missing.
Ballet is CONSISTENTLY immodest.
Shakespeare is not. And all Classical literature for that matter.
Well let us think about this.
Shakespeare was performed in its time by only male actors. Young men played the part of women. If Romeo and Juliet were played that way now, that might be a very scandalous thing to see. People are very much influenced by what other people tell them to feel.
We need to recognize what is sinful in ourselves and act accordingly.
Should no alcohol be available, because some use it to sin gravely? Worse sins come from the over consumption of alcohol than any one commits by watching a ballet.
You know what is a problem, a person will say this saint said this about dancing therefore it is bad and then turn around and say don't listen to this saint on BoD because he made an error. The Catholic Faith is consistent and constant. We have to learn the difference between things everyone has to believe and the opinions shared by certain people that is not the same for everyone in the population (alcohol, arts, etc fall into this category)
And before you decide that I don't have a clue you need to not assume my meanings, nothing I say is intended to go against God. I am a fallible woman. Ask questions to get better clarity. I don't have time to dive deep in to the intellectualism of this. I do know there are smart people out there that can and if we put aside our pride and hurt feelings we could certainly help each other become better Catholics.