Also, I have never understood why people say, “I am Catholic,” or “I am whatever.” To say you are a Christian is not enough??? It should be.
You are correct. It should be. However denominations discovered early on the value of branding, franchising and advertising . . even in the early centuries. Throw in a little "Our group is saved the others are going to Hell" and you have people jealously savoring THEIR brand of Christianity. Perhaps more than Christ Himself. The True Compass of Truth is the Bible. Not the priest. What does the Bible say?
1 Cor. 3:3 For since there is jealousy and dissension among you, are you not worldly? Are you not walking in the way of man? 4For when one of you says, I follow Paul, and another, I follow Apollos, are you not mere men? 5What then is Apollos? And what is Paul? They are servants through whom you believed, as the Lord has assigned to each his role.