Nobody taught that gospel before Luther. So are we to believe that Christ established His church, and yet nobody understood what the gospel was until Martin Luther, 1,500 years later, not even from Palestine, not even a native Greek speaker, a German speaker—I mean, he did no Greek—that somehow he understands it, where people who lived back then didn't? I mean, this would mean that the apostles were abysmal failures. They weren't able to keep the church on the right path for even 50 years after their death.
I mean, Luther's gospel is still preached everywhere today.