He who is not against us is with us.@Caino is one of many here on TOL who "do not profess the Catholic faith in its entirety" (838), but who nonetheless professes to believe in Christ, and in His Resurrection.
Nobody can formally convert to the Catholic faith without confessing our entire Creed, but anybody can come to Mass.
No Catholic is authorized to disbelieve any of what the magisterium teaches us as Apostolic. And as for who among the Noncatholics, are authentic Christians and who are not, there's an enormous spectrum of variations in particular beliefs, but all authentic Christians believe in the Lord Jesus.
By the time of the arrival of the Son on earth the religion of Judaism had become a unnessasarity overcomplicated yoke for the common Israelite.
Jesus presented a simple to understand Gospel of the Kingdom of Heaven.
After Jesus left men complicated religion again. They fight endlessly on these forums.