I am thankful that God is willing to save us even when our grasp of the gospel may be partial or defective. None of us has a comprehensive or perfect grasp of it.
Nevertheless, God’s mercy is not a warrant to neglect or deny precious truths, especially those that are at the heart of how we get right with God. And the teachers of the church (notably the Pope) will be held more responsible than others for teaching what is fully biblical.
Thus, any church whose teaching rejects the imputation of the righteousness of Christ as an essential ground for our justification would be a church whose error is so close to the heart of the gospel as to be involved in undermining the faith of its members.