ubiquitin: Chazal could make a new day for Klal Yisroel, we cannot.
If a handful (or however large or small) number of people want to make a newfangled day for them to remember an event, by all means do so and have whatever celebrations or whatever you wish. But do not expect all of Klal Yisroel or all survivors to recognize or respect or honor or do anything different on that date set by some secularists who have no love for the Torah than any other date on the calendar. We won’t impose our disagreement with it on you, and you cannot impose this date upon us. You and likeminded can have it, but don’t expect it to be recognized by others as anything other than a typical workday or playday.