The gospel is not man-centered nor is it dependent on the whims of man or his winds of doctrine which toss God's people to and fro by man's sleight whereby they lie in wait to deceive (Eph 4:14).
Instead, "All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness" (2 Tim 3:16).
Bingo. Don’t care much what Luther thought/did. Or the “Popes” for that matter. Only what is in scripture. I know what I believe, and why I believe it. I’ve read it.