Roman Catholicism gives the appearance of being the Christianity of the Bible, but it is not. The Roman Catholic Church (along with its Eastern Orthodox brethren) contains doctrines are designed to trap people within a man-made system of false worship, false teachings, vain repetitious babbling, rites, rituals, sacraments, traditions, idol worship, mysticism, occult and pagan practices, beliefs and blasphemous claims, with all of those mixed together and masquerading behind a thin veneer of pretend/fake Christianity!
The many false teachings of Roman Catholicism include (but are not limited to):
- The Eucharist being Christ’s body literally,
- Paying penance,
- Selling “indulgences” (sins),
- Pope as god on earth (blasphemy),
- Mandated celibacy,
- Salvation is earned by “meritorious acts,”
- Other man-made rituals, ordinances, sacraments and deceptions, which are too long to even list here.
For many hundreds of years, the Roman Catholic Church worked to suppress the truth of Scripture, even corrupting Scripture (in the form of the Latin Vulgate) to support church doctrines. This “church” even tortured and massacred those who would dare to translate the Bible in their own language, or even just read it in their own language! It is understandable that many people were deceived by the Church of Rome during the dark ages, as the truth of Scripture was withheld from the common man, but with abundant access to the truth of God’s Word today, I’m not sure how anyone mistakes Roman Catholicism for true Christianity as defined in Scripture.
Keep in mind that Roman Catholicism evolved out of mixing pagan beliefs with elements of Christianity, and Catholicism began hundreds of years after Christ. Part of the deception is their claimed association with the early saints and apostles such as Peter and Paul, giving the appearance that they were in fact the first Christian church. In an excerpt from The Christian Church, It’s Rise and Progress, H. M. Riggle helps shed more light on this by comparing the true church of the New Testament (the one universal Church of God, the Church of Christ) vs. the Church of Rome: 
The apostate church is brought to view in Revelation 17 under the symbol of a corrupt woman having a golden cup in her hand, full of abominations and filthiness of her fornications. She is called “Babylon the great, the mother of harlots.” This corrupt woman is not the (pure) bride of Christ. There is no communication with the living head (Christ). She apostatized— separated from the truth, played the harlot— and at last she will have her portion in the lake of fire and brimstone. This is the great apostasy.
The Primitive Church and the Church of Rome Compared
The true church is characterized by its receiving and retaining the doctrine and faith of the apostles. It is “built upon the foundation of the apostles and prophets, Jesus Christ himself being the chief cornerstone” (Eph. 2:20). “And they were persevering in the doctrine of the apostles” (Acts 2:42). The church must hold the same doctrines which the inspired apostles and prophets taught, and which are contained in the Holy Scriptures. This is the test laid down by Jesus himself: “My sheep hear my voice: . . . and they follow me”; “A stranger they follow not.” Hear the apostle on this point: “Whosoever revolteth, and continueth not in the doctrine of Christ, hath not God. He that continueth in the doctrine, the same hath both the Father and the Son.”
It is not, then, the sentiments of fathers, or pontiffs, or bishops, or councils, but only those of prophets and apostles, that constitute the foundation of the church’s faith. Its apostolic doctrine is the first test of the church, which is emphatically entitled “the pillar and ground of the truth.” If this quality is wanting, nothing else can avail.
The Church of Rome fulfils the prediction of Paul that “some shall depart from the faith, giving heed to spirits of error, and doctrines of devils” (1 Tim. 4:1). She has departed from the apostolic doctrine that salvation is obtainable through repentance faith (Mark 1:15; Rom. 4:16; Rom. 10:9; Eph. 2:8, 9) and substituted a religion of works, including indulgences, the confessional, mass, extreme unction, purgatory, etc. Not a single one of these has any foundation in Holy Writ.
She has departed from the apostolic doctrine of holiness of heart and life (Matt. 5:8; Tit. 2:11, 12; Luke 1:74, 75; 1 John 4:17; 1 John 3:3, 6) and substituted a mere external holiness, which she has restricted to certain orders and individuals, such as monks, nuns, sisters of charity, prelates, and popes; thus has come the appellation, “His Holiness the Pope.” In the primitive church all the brethren were holy, because they were saved from sin.
She has departed from the apostolic doctrine of a sinless life (1 John 3:6, 8, 9; 1 John 5:18), and in the following quotations from her standard authors acknowledges and teaches that her members are full of sin. In fact, a sinless life is nowhere taught by the priesthood of Rome.
The Call to Leave Babylon
We have seen that “Babylon the great” of Revelation 17 consists of a family, a mother and her harlot daughters. The mother is the Church of Rome, while the daughters are in particular the Protestant sects. This fraternity of so-called churches, from Rome down to the latest born daughter, does not represent the pure bride, “the Lamb’s wife.” Of his bride the Lord said, “Thou art all fair, O my love, and there is not a spot in thee.” “One is my dove, my perfect one is but one.” “And it is granted to her that she should clothe herself with fine linen, glittering and white. For the fine linen are the justifications of saints.” “That I may present you as a chaste virgin to Christ.” God has but one family, his household. Since no man can rightly have two families, God has but one church, which is the holy family.
Ignorantly many honest souls, as well as true children of God, have been led to join these apostate institutions. We do not doubt that the Church of Rome holds within her fold many sincere and honest people whose hearts are longing for better things. We have a warm and tender feeling for these dear people. It is not them that we antagonize, but the apostate, corrupt religion and teaching that is destroying their souls.
There are many books and resources which discuss the errors of Roman Catholicism in greater detail, so please seek them out.
 Riggle, H.M. (1912), The Christian Church, It’s Rise and Progress, (The Gospel Trumpet Company).