Original sin - an essential truth of the faith
The doctrine of original sin is, so to speak, the "reverse side" of the Good News that Jesus is the Saviour of all men, that all need salvation and that salvation is offered to all through Christ. The Church, which has the mind of Christ, knows very well that we cannot tamper with the revelation of original sin without undermining the mystery of Christ.
Source: Catechism of the Catholic Church (Vatican.va)