You're right when you state,
This is the catholic faith One cannot be saved without believing it firmly and faithfully.
However, Bible believing Jesus loving Christians baptized, not sprinkled, and indwelt by God's holy spirit are saved by grace through faith in Christ Jesus. Not through faith in the Catholic church, not through faith in the Trinity teachings of the Catholic church.
Jesus never spoke of the Trinity. When that teaching came into the Bible over a thousand years after Christ returned to heaven, it is a man made convention, not that of Christ.
How Trinity entered the church in 325 AD at the Council of Nicaea.
The old testament tells us, our God is one! Jesus said, I and the Father are ONE! Not three!
Jesus said to baptize in the name of himself, Jesus Christ. Later, collaborative with the introduction of the Trinity was the additional scripture, baptize in the name of the
father, the son, and the holy spirit, added. When in truth, God is spirit (we must worship in spirit) and is holy. Not a second dimension to God at all. Jesus was God. (and you shall name him Emmanuel, meaning God with us.) . It's one God forever and always. Not three natures, not three separate
persons. God is not a person, God is holy spirit.
edit, deleted emote that appeared with punctuation in place.