Attending catholic mass is not a commandment in my Bible or any other. There are many ways to keep the Lords day Holy. Attending the service of a particular denomination every Sunday will not save you no matter how highly the denomination thinks of itself. But Luther certainly lives rent free in your head. Maybe if you study what he said/did you might learn something.
For Catholics — Keep holy the Lord’s Day — means attending Mass.
Please don’t try to tell us what to believe.