You provided some interesting quotes from the CCC but seemed to overlook some other ones. Let’s go back to paragraph # 816 of the Catechism of the Catholic Church where we read, “The Second Vatican Council’s Decree on Ecumenism explains: ‘For it is through Christ’s Catholic Church alone, which is the universal help toward salvation, that the fullness of the means of salvation can be obtained. It was to the apostolic college alone, of which Peter is the head, that we believe that our Lord entrusted all the blessings of the New Covenant, in order to establish on earth the one Body of Christ into which all those should be fully incorporated who belong in any way to the People of God.’” (C.C.C. # 816)
As stated, not only is salvation found in the Catholic Church, but also the “fullness of the means” of salvation.
So, exactly what does this mean? Well, to receive the free gift of salvation, Catholics must until their last breath, maintain the righteousness that they received during the Sacrament of Baptism. Ongoing righteousness is maintained through the reception of the Sacraments of Confession and the Holy Eucharist. While belonging to the invisible Body of Christ, Catholics recognize that they absolutely need the Sacraments of the visible Body of Christ, the Catholic Church, as their assurance of righteousness and salvation. Hence, believers require the Catholic Church as the “fullness of the means of salvation.”
In the case of non-Catholic Christians, while through faith in Jesus and the Sacrament of Baptism, they are admitted into the invisible Body of Christ as their first instalment towards salvation, once they have committed mortal sins, they possess NO means of reinstating the righteousness that they had originally received during the Sacrament of Baptism. Such a status holds serious consequences, the unrighteous sinners being unable to enter the Kingdom of Heaven.
Within the Catechism of the Catholic Church, it states, “If (mortal sin) is not redeemed by repentance and God’s forgiveness, it causes exclusion from Christ’s kingdom and the eternal death of hell, for our freedom has the power to make choices for ever, with no turning back.” (C.C.C. # 1861)
What are these mortal sins that can impede one’s entry into the Kingdom of God? In the Letter to the Galatians, we read, “Now the works of the flesh are plain: fornication, impurity, licentiousness, idolatry, sorcery, enmity, strife, jealousy, anger, selfishness, dissension, factions, envy, drunkenness, carousing, and the like. I warn you, as I warned you before, that those who do such things shall not inherit the Kingdom of God.” (Gal. 5:19-10; C.C.C. # 1852)
In the First Letter to the Corinthians, we read, “Do you not know that wrongdoers will not inherit the Kingdom of God? Do not be deceived! Fornicators, idolaters, adulterers, male prostitutes, sodomites, thieves, the greedy, drunkards, revilers, robbers - none of these will inherit the Kingdom of God.” [1 Cor. 6:9-10]
Two Chapters later, we read, “Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be answerable for the body and blood of the Lord. Examine yourselves, and only then eat of the bread and drink of the cup. For all who eat and drink without discerning the body, eat and drink judgment against themselves. For this reason many of you are weak and ill, and some have died.” [1 Cor. 11:27-30]
In the Revelation to John, we read, “Those who conquer will inherit these things, and I will be their God and they will be my children. But as for the cowardly, the faithless, the polluted, the murderers, the fornicators, the sorcerers, the idolaters, and all liars, their place will be in the lake that burns with fire and sulphur, which is the second death.” [Rev. 21:7-8]
“Outside (of the Kingdom of God) are the dogs and sorcerers and fornicators and murderers and idolaters, and everyone who loves and practices falsehood.” [Rev. 22:15]
These Biblical passages declare that, Catholic or not, those who chose through their free will to turn away from the holy ways, the righteousness of God, because of their mortal sins, they eternally condemn themselves.