Jesus never wore a top hat and tuxedo. If you wear these things on formal occasions, does that mean that you are not acting in a Christ-like manner and that it would be appropriate to question your Christian commitment? Our Christian commitment is not demonstrated by wearing exactly the clothes that Jesus would have worn but by imitating his example of holiness.
In the pope’s case, he ordinarily wears a simple robe called a cassock and a cap called a zucchetto. For special occasions, such as when he celebrates Mass, he wears a formal robe called a chasuble and a headdress called a miter. These clothes signify his status as Christ’s vicar and honor the occasions on which he wears them, much as our clothing signifies our state in life and honors the occasions on which we wear them. If it is okay for ordinary Christians to wear clothing for such reasons, it is okay for the pope to do so.