I think it is up to each individual as to which religious practices they wish to partake in. As long as they keep the practice to themselves, and do not expect others to either join in or change how they behave towards the person, then it is down to individual freedom of behavior.
Many religions have practices that are core to its set of beliefs. These practices are the basis and foundation of the religion and provides parishioners with a way of actively participating in their religious belief system. The practices enable people to identify themselves with their religion through a practice of their belief. These practices should not be retired as retiring them may lead to the watered down and less identifiable religion.
No, some religious practices like Ash Wednesday should not be retired, because it is a good practice. The purpose of Ash Wednesday is to remind ourselves that we are mortal. From ashes to ashes, so they say. What is the harm in remembering that? We need to remember that so our lives have purpose.
To say that a religious holiday should be dropped because one person finds no value in it seems wrong to me. Ash Wednesday, I would presume is still followed by many in the Christian faith. The secularization of America does not mean that these practices have lost favor with true Christians.