The most crucial problem with the Roman Catholic Church is its belief that faith alone in Christ is not sufficient for salvation. The Bible clearly and consistently states that receiving Jesus Christ as Savior, by grace through faith, grants salvation (John 1:12; 3:16,18,36; Acts 16:31; Romans 10:9-10,13; 1 Corinthians 15:1-4; Ephesians 2:8-9). The Roman Catholic Church rejects this. The official position of the Roman Catholic Church is that a person must believe in Jesus Christ AND be baptized AND receive the Eucharist along with the other sacraments AND obey the decrees of the Roman Catholic Church AND perform meritorious works AND not die with any mortal sins AND etc., etc., etc. Catholic divergence from the Bible on this most crucial of issues, salvation, means that yes, Catholicism is a false religion. If a person believes what the Catholic Church officially teaches, he/she will not be saved. Any claim that works or rituals must be added to faith in order for salvation to be achieved is a claim that Jesus’ death was not sufficient to fully purchase our salvation.
While salvation by faith is the most crucial issue, in comparing Roman Catholicism with the Word of God, there are many other differences and contradictions as well. The Roman Catholic Church teaches many doctrines that are in disagreement with what the Bible declares. These include apostolic succession, worship of saints or Mary, prayer to saints or Mary, the pope / papacy, infant baptism, transubstantiation, plenary indulgences, the sacramental system, and purgatory. While Catholics claim Scriptural support for these concepts, none of these teachings have any solid foundation in the clear teaching of Scripture. These concepts are based on Catholic tradition, not the Word of God. In fact, they all clearly contradict Biblical principles.
In regards to the question “Are Catholics saved?”, this is a more difficult question to answer. It is impossible to give a universal statement on the salvation of all members of any denomination of Christianity. Not ALL Baptists are saved. Not ALL Presbyterians are saved. Not ALL Lutherans are saved. Salvation is determined by personal faith in Jesus alone for salvation, not by titles or denominational identification. Despite the unbiblical beliefs and practices of the Roman Catholic Church, there are genuine believers who attend Roman Catholic churches. There are many Roman Catholics who have genuinely placed their faith in Jesus Christ alone for salvation. However, these Catholic Christians are believers despite what the Catholic Church teaches, not because of what it teaches. To varying degrees, the Catholic Church teaches from the Bible and points people to Jesus Christ as the Savior. As a result, people are sometimes saved in Catholic churches. The Bible has an impact whenever it is proclaimed (Isaiah 55:11). Catholic Christians remain in the Catholic Church out of ignorance of what the Catholic Church truly stands for, out of family tradition and peer pressure, or out of a desire to reach other Catholics for Christ.
At the same time, the Catholic Church also leads many people away from a genuine faith relationship with Christ. The unbiblical beliefs and practices of the Roman Catholic Church have often given the enemies of Christ opportunity to blaspheme. The Roman Catholic Church is not the church that Jesus Christ established in his heavenly ministry through the Apostle Paul. And while Jesus’ words in Mark 7:9 were directed towards the Pharisees, they accurately describe the Roman Catholic Church as well,
“You have a fine way of setting aside the commands of God in order to observe your own traditions!” source