This is the bottom line. Even those of us who know and care and try have to be reminded over and over again. On these topics the priests have to repeat themselves probably twice a year in every parish and not walk on eggshells.
Maybe. I think that some of them have just resigned themselves to it being a losing battle. My elderly independent priest reminds women of the dress code several times a year. Each time there's some improvement for about a week or two, but then back to the same old same old. So more than this (a bi-annual reminder) is needed. Short of pounding the pulpit on an almost-weekly basis and refusing the Sacraments to the offenders, the reminders by themselves won't be effective. What's funny with the women is that all it takes for ONE woman to get away with a short skirt, and the very next week you see a dozen more ... as the trailblazer had gotten away with it, probably secretly being considered a hero by the others.
Refusing the Sacraments can be problematic. Sure, there are the obvious egregious cases. But what about infractions that are either borderline or less grave? Do you have old ladies policing the entrances with measuring tapes? That can lead to a very bizarre cult-like environment for Mass. So it's almost like a no-win. If the priest cannot persuade the ladies to WANT to be modest and to embrace it, it's an impossible battle, and some priests have just given up. Not that they don't care necessarily, but they've given up and feel that there's nothing more than they can do.