It has been said the Galatians were amateurs compared to the modern day Roman Catholic Church. While the Apostle Paul rebuked the Galatians for adding circumcision to faith in Christ and thus negating the gospel, the Roman Catholic Church has added hundreds of rituals and beliefs to the gospel. From the Marian dogmas especially as her being sinless and therefore the mediatrix between man and God and her being the mother of God, to the priesthood and the priest as being the alter Christus (as acting in the place of Christ) as he calls down the person of Christ from heaven and sacrifices him every Sunday in the Eucharist by which God is placated and the priest's office as the intercessor of man's prayers so that through the priest they are offered up to God, to purgatory and the intermediate state whereby man is purged of his remaining sin, to indulgences whereby a person can purchase righteousness for those who are in purgatory from the overflow of merit be it Christ's, Mary's or the Saints, to the belief that faith alone does not save but it is faith and works that save, to the Pope and his title as the Vicar of Christ (Christ's representative on earth and the direct successor of the Apostle Peter) whereby when he speaks ex cathedra he speaks infallibly as the very voice of God , to the Roman Catholic magisterium as giving the sole infallible interpretation of the bible and as it not being the sole source of Christ’s teaching but that there is a double rule of faith, namely, Bible and Tradition. Tradition being the sum of revealed doctrine which has not been put down in Sacred Scripture but has been handed down to the Church from age to age. It is this belief that the bible is not the sole source of Christ's teaching and the appeal to Tradition that allows all sorts of modern Catholic beliefs to be defended even if they are not found in Scripture.
In view of all this, which is not taught in Scripture and which are direct attacks on the authority of Scripture, the personhood of Christ and his substitutionary atonement, and the grace of God which is sufficient to save, modern day Catholicism is not only not a denomination of Christianity but falls outside Christianity all together. Sadly many Christians today do not view these heresies with the seriousness that they need to be. Those who speak out against modern day Roman Catholicism are often seen as eccentric voices in the wilderness. Yet since the time of the reformation, when Martin Luther then John Calvin rallied against the teachings of the Roman Catholic Church, those teachings have only become more heretical not less. And yet many today view the divide between the Roman Catholic Church and Protestantism as being slight and minor. But I view the beliefs of the Roman Catholic Church as being so serious that if a person believes them and therefore follows them they are walking down a path that will lead them to hell. This is therefore serious because it is a matter of the gospel and a person's soul. (Romans 1:16-17) It is a matter of how a sinful person is saved and reconciled to a holy God. (Ephesians 2:13-16) It is a matter, not of the necessity of grace, but of the sufficiency of grace to save. (Ephesians 2:8-9) It is a matter of the sufficiency of Christ's death to save to the uttermost those who would draw near to God and his intercession for them. (Hebrews 7:22-25)