Salvation is by faith alone. That is a core doctrine of the Christian faith that the RCC denies.
It is said that, "Sola Fide, and Sola Scriptura are the two pillars of the Protestant Reformation. The other two branches of Christianity, The Catholics and the Orthodox don't hold to them
This much it true - it's why the Reformers rejected the false teaching of the Roman Catholic church
and the same "sombody" said, "As such then they are only 500 or so years old. So they aren't "core doctrines." In fact, on the church history timeline, they're relative late comers.
Let's look to Scripture first.
Being justified freely by his grace through the redemption that is in Christ Jesus,” (Rom. 3:24).
“For by grace are ye saved through faith; and that not of yourselves: it is the gift of God,” (Eph. 2:8).
“Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost,” (Titus 3:5).
Contrast that with Trent: “If any one saith, that man is truly absolved from his sins and justified, because that he assuredly believed himself absolved and justified; or, that no one is truly justified but he who believes himself justified; and that, by this faith alone, absolution and justification are effected; let him be anathema.” If you believe the Bible, Trent says, "let you anathema."
“For what saith the scripture? Abraham believed God, and it was counted unto him for righteousness,” (Rom. 4:3).
“Therefore being justified by faith, we have peace with God through our Lord Jesus Christ,” (Rom. 5:1).
Trent: Canon 24: “If any one saith, that the justice received is not preserved and also increased before God through good works; but that the said works are merely the fruits and signs of Justification obtained, but not a cause of the increase thereof; let him be anathema.”
“Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage. Behold, I Paul say unto you, that if ye be circumcised, Christ shall profit you nothing. For I testify again to every man that is circumcised, that he is a debtor to do the whole law,” (Gal. 5:1-3).
Trent: Canon 30: “If any one saith, that, after the grace of Justification has been received, to every penitent sinner the guilt is remitted, and the debt of eternal punishment is blotted out in such wise, that there remains not any debt of temporal punishment to be discharged either in this world, or in the next in Purgatory, before the entrance to the kingdom of heaven can be opened (to him); let him be anathema.”
Which will you believe? (imagine a balance scale, the magisterium on one side, God on the other)
As for the um..."miscommunication" that Sola Fide is a latecomer...let's look to early church writings.
CLEMENT of Rome: "All the ancient fathers descended from Abraham, both before the Law and under the Law, were glorified and magnified, not through themselves, nor through their works of righteousness which they had done, but through His will. Therefore we, also, being called through His will in Christ Jesus, are not justified through ourselves, neither through our own wisdom, or understanding, or piety, or works which we have done in holiness of heart, but through faith, that faith through which the Almighty God hath justified all that ever lived; to whom be glory for ever, Amen!"
IGNATIUS (1ST CENT): "To me, Christ is in the place of all ancient muniments. For His Cross, and His death, and His resurrection, and the faith which is through Him, are my unpolluted muniments; and in these, through your prayers, I am willing to have been justified."
[Letter to the Philadelphians]: "The prophets also do we love, because they have announced the Gospel; and they hoped in him and awaited him. In him and by their faith in him they were saved, being united to Jesus Christ."
POLYCARP OF SMYRNA (AD 69-156) [in his letter to the Philippianss, ch. 1:3]: "Knowing that 'you are saved by grace, not because of works' (cf. Eph. 2:5, 8, 9), namely, by the will of God through Jesus Christ"
"The Lord Jesus Christ, who endured to submit unto death for our sins; whom God raised up, having loosed the pains of hell; in whom ye believe, not having seen Him, but believing ye rejoice with joy unspeakable and full of glory.... knowing that through grace ye are saved, not of works, but by the will of God, through Jesus Christ."
JUSTIN MARTYR: [Dialogue with Trypho, ch. XCII]: "For Abraham was declared by God to be righteous, not on account of circumcision, but on account of faith"
AMBROSE: "Without the works of the Law to an ungodly man, that is to say, a Gentile, believing in Christ, his 'faith is imputed for righteousness,' as also it was to Abraham. How, then, can the Jews imagine, that through the works of the Law they are justified with the justification of Abraham, when they see that Abraham was justified, not by the works of the Law, but by faith alone? There is no need, therefore, of the Law, since through faith alone, an ungodly man is justified with God."
CHRYSOSTOM (4TH CENT) [homil. de fide.] "If you believe faith, why do you bring other things in, as though faith alone sufficed not to justify?"
[2 ad Eph. serm. 5]: [speaking of the thief on the cross] "I can shew a faithful man without works... only faith by itself saved him."