Modesty is an attitude, not a style of dress. The idea that your body is so amazing that men will be driven to lust because you wore a skirt cut 2" above the knee is contrary to modesty.
Adam and Eve were unfallen and could look at each other without lust. Today people are fallen. Being used to immodesty and desensitized doesn't make something modest. A Pope last century said that modesty should be based on the MOST virtuous culture, - one that is not desensitized to it, but one that values it. This means that what our culture considers modest might not be actually modest. It's not all subjective.
What is this "most virtuous culture" that you speak of? Do the tribal groups that do not cover their genitals but do practice permanent marriages with sexual activity only present inside of marriage lack virtue? Would greater "modesty" benefit them in some way? I'd suggest that they, in terms of cultural virtue related to physical appearences are far and away ahead of our culture in the US, or the culture present in the US 150 years ago, or the culture in ME countries where burkhas are the norm.
Fallen human beings might look at other human beings as objects if they're not covered in the way that they should be. Why tempt them to this? If I tempt a guy, I've sinned, by introducing that battle into his mind, even though it's up to him to make the ultimate choice of saying 'yes' or 'no'.
You know what I think is hot? Like, really gets me going? Head coverings at Mass. On an even average girl, rawr. I've had this discussion with other men and I know I'm in good company. Armed with this knowledge, how will you proceed?
The Catechism says that modesty protects the intimate center of the person. Why show everything to everyone? the body is meant to be seen by one's spouse. If a girl in a bikini was walking on a street, wouldn't men have impure thoughts?
99 times out of 100, no. A simple woman walking in a bikini is not going to give men impure thoughts, especially in those areas where it is the norm. A very, very small percentage of women might look appealing enough in a bikini to warrant a second look, and even fewer to cause a typical man to lust uncontrolably. The woman who is that attractive will likely get that response from men no matter what she wears, short of something silly like a burka or ankle-length denim skirt.
God's creation is good. But we have concupiscence which leads to sin. If a girl dresses immodestly, guys aren't going to look at her like Adam looked at Eve.
That's all well and good, but you cannot deny the effect that the cult of modesty has had on savage cultures. Our land, where a woman may wear virtually whatever she pleases without expecting cat-calls, groping or worse from the men she crosses paths with is far superiort to those cultures which strongly value keeping women covered because they're just so attractive that the men couldn't handle it. I talked earlier about my friend in Finland who quickly grew comfortable taking nude saunas with his wife's family and their neighbors of all ages, male and female. He unlearned what he had unthinkingly grown to accept as fact in the US - that uncovered ladybits are automatically arousing without regard to context. He is in a better place now, finding arousal with his wife at appropriate times and in the right context and not in others.