The Reader's Digest version of this is that the Catholic Church has incorporated the name of Jesus Christ while keeping the pagan rituals of it's true heritage.
Co 11:2 For I am jealous over you with godly jealousy: for I have espoused you to one husband, that I may present you as a chaste virgin to Christ.
This is being spoken to the elect, not the many called, if we seek or should I say are chosen for the 1st Resurrection the above scripture speaks volumes.
2Co 11:3 But I fear, lest by any means, as the serpent beguiled Eve through his subtlety, so your minds should be corrupted from the simplicity that is in Christ.
The Catholic Church with it's continual sacrifice of "Christ" in the communion sacrement is constantly every day in every mass telling the parish that Jesus death at the cross was insufficient, that the "Church" and it's temporal communion ceremony must be repeated for salvation. Also, what to make of confessing your sins to a man, and that man gives you a penance to forgive you your sins.
2Co 11:4 For if he that cometh preacheth another Jesus, whom we have not preached, or if ye receive another spirit, which ye have not received, or another gospel, which ye have not accepted, ye might well bear* with him.
* ἀνέχομαι
anechomai
an-ekh'-om-ahee
Middle voice from G303 and G2192; to hold oneself up against, that is, (figuratively) put up with: - bear with endure, forbear, suffer.
Are we to bow before idols? To worship Mary (mother of Jesus) and the apostles? Should we pray to them? Ask them to intercede for us to God? Should we pay tributes ($$$) to the church to bail our loved ones out of pergatory? Are we to believe God's nature is to burn unbaptized children in hell for eternity? Is the pope infallible? What is the origin of all the Catholic Holidays (holy days)? Is this "another Jesus" being preached? Please show me where the apostles were preaching the above.
The Catholics are not alone, Protestantism has taken much of Catholicism into it's midst, why do most Protestants worship on Sunday and not the Sabbath, the 7th day (sundown Friday through sundown Saturday)? Why do they celebrate the holidays like Christmas, Easter, etc.
The churches do provide milk for the called and chosen alike, but once one is spiritually converted milk is no longer desired and the strong meat of the Word is sought.
I was raised Catholic and I have known many decent people who attended their whole lives, I saw with my own eyes these sincere folks whose focus was on "the church" and it's false doctrines more than "the Living Lord," there is so much more.
Ray and Mike write extensively on this subject explaining these things much more efficiently and in depth than I am capable of, this "another Jesus" stuff should not be taken lightly, I strongly suggest this material be read and to gird ourselves from the beguiler.