This is what it amounts to. It is all well and good to enter into a debate with RCs so as to refute their arguments. There is no point being ignorant about what they teach. But once their arguments are refuted the outcome is that they teach a man offers Christ to God to atone for their sins, thus rendering the sacrifice of Christ insufficient.
It is more helpful to view Roman Catholicism as a "mediated" system of religion. At every step, Rome places its institutions, people, and regulations between the professing believer and God.
True faith teaches that God imparts grace directly to believers. Rome teaches that this grace is mediated through the church and through its sacraments.
True faith teaches that we pray to God and God alone. Rome teaches that we pray to the saints and the saints deliver our prayers to God.
True faith teaches that we are the body of Christ. Rome teaches that it is the body of Christ and that it dispenses Christ's blessings on his behalf to those who follow it.
True faith teaches that God works how, when, and where he wills, ordinarily using means. Rome teaches that by the means it has ordained, the fountain of God's grace is turned on and off at the beck and call of men through the intrinsic efficacy of sacramental acts.
True faith teaches that it is God who sustains us in our Christian walk. Rome teaches that as long as our actions remain in faithful accord with church teaching, the church will sustain us in our Christian walk.
Rome is a kidnapper of souls - a guardian entrusted with their guidance who steps into and usurps the parental role.
If you view Roman Catholicism through this lens - that it is a mediated system of religion - the whole thing makes a great deal of sense. You can read the Catholic Catechism and various papal encyclicals and see the internal consistency and logic of it all - a consistency that extends even over the seeming contradictions of Trent/Vatican I/Vatican II. Rome places itself squarely between you and God, in the process usurping the place of both - denying you your place in the priesthood of all believers by arrogating to itself and its institutions those prerogatives which God has granted to all believers, and denying God his place in the life of all believers by arrogating to itself and its institutions those prerogatives which God has claimed as his own. It is impressively thorough and comprehensive in the consistency with which it takes every available opportunity, leaving no stone unturned, to insert steps between the believer and God, and countless hours and bottles of ink have been expended by some of the greatest minds in the history of the west to the end of exhaustively fleshing out this system of mediation to the very last degree. The stated goal is to "help" the believer, but given the nature of true faith, this help is actually a disastrous hindrance.
It is this mediated aspect of Roman Catholicism that explains why it is qualitatively different from Mormonism or Hinduism. In the Catholic system, it is the true God that is on the other side of all that... stuff. The goal of Rome is to keep you from God, but in spite of its best efforts, he can sometimes be glimpsed through the smoke, if much of the time by accident. But because it is the true God on the other side, some in this system can be saved. That's not something that can be said about Mormonism, Hinduism, Islam, or any overtly non-Christian religion.
Another helpful way to view the Roman system (though not nearly as significant as what I stated above) is that it is a system with an underdeveloped theology of the Holy Spirit. Rome got off the train, so to speak, before the great developments made by Protestantism (and particularly the Reformed) in parsing out the work of the Holy Spirit in the Christian life. As a result, the only thing that Rome can envision standing in the place that should be occupied by the Holy Spirit is... Rome. Everything that Rome attempts to do in the life of the believer is something that ought properly to be the role of the Spirit. This incidentally explains why Roman Catholicism can have such a pronounced charismatic strain and why some of their "miracle stories" are so strange (like the ability of Thomas Aquinas to levitate).
It is the immediate nature of Reformed theology that to me is one of its most appealing aspects and one of the best indicators that it is in accord with Scripture; and conversely the mediated nature of Roman theology that makes it so appalling and utterly unbiblical. When I ponder that I have direct access by the Spirit through the Son to our heavenly father himself - with the helps of fellowship, ministry, the sacraments not as standing between me and God but as gifts also given directly by God to prop me up and sustain me on the long and wearying journey toward my heavenly home - and when I ponder that Christ himself is sitting in heavenly session at God's right hand, pleading for me day in and day out - and when I ponder that the Holy Spirit himself groans with my every cry: there is really no clear choice. Roman Catholicism has absolutely nothing comparable to offer. In place of a direct word of forgiveness from Christ they put the cheap substitute of a priest's absolution; no wonder there can be no real assurance of salvation. In place of the mysterious way in which the Holy Spirit works through baptism and communion they have their horrid mechanical reductions of these acts to.a man-directed system. In place of the reassurance which the Spirit grants to wounded souls, they have the confessional booth and a dictum to go say 10 Hail Marys or whatever.