Having Good Middos and acting like a Mentsh is a Mitzvah.
(Derech Eretz Kadma L’Torah.)
Keeping Tznius is a Mitzvah.
Keeping Shabbos is a Mitzvah.
Keeping Kosher is a Mitzvah.
No one is disparaging previous generations, because they did not know any better or because they had to deal with issues that we don’t have to deal with today. No one is saying that a person does not need Good Middos and is allowed to C”V commit a Chillul Hashem.
All that is being said is that for a Jew to keep Yiddishkeit properly, ALL of the Mitzvos must be observed.
Acting in a Tznius-dik manner while dressing in a non-Tznius-dik manner does not make a girl Tznius-dik. Both types of Tznius must be observed.
IY”H there should be a way to educate girls and women about Tznius, in a non-confrontational manner that teaches about the rules and rewards of Tznius, and the punishment for the lack of Tznius, C”V.