The argument against pants is for the most part two-fold, one of gender blurring, and one of temptation. And modesty is more than that which does not tempt, it is a part of avoiding the above and more.
Simply because there are pants that can be less immodest than other pants does not make pants in fact, modest for women truly, ever. Someone uses the term ‘modest pants’, but that is only relative to something even more immodest, they aren’t truly.
Yes you can get objective measurements and standards as to what clothing is tempting, immodest, gender inappropriate, or not, that has always been the case for the Church, and for people in general. It is not all relative.
People react to the immodest… then like frogs in ever growing hot water, they do not because they are immersed in it and have lost a sense of shame. That is the main reason it appears relative to some.
Right now we live in a culture where people are raised with as little sense of shame about clothing as possible. There are not formal standards, and people look very different in how they dress and behave than in other times.
If I look at pictures of how children were dressed a little while ago, they looked like little young men and ladies, they were not immodestly dressed at all.
Now clothing is not made for modesty but for simple ease of wear and for attracting attention, the opposite of modesty.
And so, from childhood to adulthood we are today soaked in immodesty and have not the proper sense of shame for it. If we did, then we could more easily individually perceive the standard that the dress of a certain length, etc. provides.
That we do not, we should not take as moral license to dress badly, simply because of our malformed feelings about the matter. That is what conversion is for. We learn the truth and we change our feelings, we do not apply our feelings to change the truth.
People who are more degenerate than others, cannot be as excited by what would normally excite them if they were modest and restrained. The more a pleasure seeker you are, the more pleasure you need to be aroused generally. Like drugs, the more you have the more you need to get high.
So, the arguments against modesty based on some people being possibly hypersensitive are mostly flawed. Yes there are such people, but in fact what is normal right now is insensitivity towards a good deal of what is in a lesser way immodest – because we live in an immodest culture and are soaked in it from birth onwards.
So, if men sometimes are not attracted to or ignore women who dress like prostitutes did in the past, but is everyday now – does not mean the women are not dressing immodestly (however unconsciously). It means these men are of the group that is very used to immodesty, and have not yet practiced enough modesty in their own selves to realize what is immodest or modest.
If everyone is going around in bikinis and someone wears a full swimsuit, this isn’t really more modest, it’s just slightly less immodest. That men who do not practice chastity are more likely to react to the bikini than other men is simply a sign of their degeneration, not the modesty of a full swimsuit.
But men in general will not be troubled by a modestly dressed woman in loose clothing that has a skirt below the knees. Then truly, if they have troubles it is particular to them as individuals and more exceptional temptation.
More like some of the 30s… but for the large part 40s and 50s. Such as more emphasis on jackets, coats and hats, and knee length dresses and skirts or longer. Definitely not the flappers 
