"I'll be justified by faith in Jesus, but not faith in the RCC, thank you."
Right. So will I and am I am Catholic. You still don't understand.
Some Christians are catholic, not all catholics are Christian. It's a condition of the heart.
One thing I will agree on, just because one is Catholic doesnt mean anything. Too many people have an external devotion, they go to Church because its habit, they haven't grown in grace, or internalized their religion. "You have become lukewarm so I will spit you out of my mouth"
I believe that it is a constant daily struggle/and joy to strive for perfection. "Be ye perfect as your Heavenly Father is perfect"
We have to advance in virtue, daily.