I think people are misunderstanding the concept of takkanos today at least in the non-Chassidic world. The idea is not necessarily that there is an evil in our midst which needs to be expunged. It is more that the peer pressure of society allows us to be sucked into many mishugasin which become very difficult to stop once they are started. It is extremely unreasonable to expect people to have the strength to fight against it on their own. The idea of takknos says “Hey we all agree that this is ridiculous and that it is killing us. Can we as a community all agree to cut it out?” Then the Rabbis sign their name to it as if to say congratulations for having some sense.
This gowns thing is a perfect example. All these kallahs who “suggest” the color that everyone should wear is in a sense pressuring families to tack on one more unnessary expense in addition to the headache of finding the “right” gown. All we need to do is tell the kallahs to cut it out. Don’t suggest anything and instead please just tell your frinds and relatives to come as you would like. Have your fun in some other way that does not harm anyone. No threats ordecrees are necessary. Just someone to speak up and say enough already!