Like it or not, Princess has changed from the formal cruise line that it use to be in order to survive.
Expecting a cruise line to remain stagnant just to fill the desires of what has become a minority, isn't going to happen. In this transitional period they now are being lenient about accepting everyone dressed as they choose.
Either accept what they've become today or move on to a cruise line that better suites your desires, like P and O, Cunard or Seaborn.