Many people mistakenly believe that the Immaculate Conception refers to the conception of Jesus Christ. Jesus’ conception was most assuredly immaculate—that is, without the stain of sin—but the Immaculate Conception does not refer to Jesus at all. The Immaculate Conception is a doctrine of the Roman Catholic Church in regards to Mary, Jesus’ mother. The official statement of the doctrine reads, “The blessed Virgin Mary to have been, from the first instant of her conception, by a singular grace and privilege of Almighty God, in view of the merits of Christ Jesus the Savior of Mankind, preserved free from all stain of original sin” (Pope Pius IX, Ineffabilis Deus, December 1854). Essentially, the Immaculate Conception is the belief that Mary was protected from original sin, that Mary did not have a sin nature and was, in fact, sinless.
Read more: https://www.gotquestions.org/immaculate-conception.html
Was Mary sinless? - GotQuestions
Is the perpetual virginity of Mary biblical? - GotQuestions
The Roman Catholic Church’s unbiblical doctrine of Mary is a definite problem to be sure, but it’s not the most crucial problem.
“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; 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.” - See: Is Catholicism a false religion? Is Catholicism a cult? - GotQuestions