And thankfully Catholic Christians understand that the word catholic can also mean the universal Christian church, not just those of the Pope or the Patriarchs...
You wrote:
“And thankfully Catholic Christians understand that the word catholic can also mean the universal Christian church, not just those of the Pope or the Patriarchs...”
No, actually orthodox Catholics understand that the only catholic church is the Catholic Church.
4. The Church’s constant missionary proclamation is endangered today by relativistic theories which seek to justify religious pluralism, not only de facto but also de iure (or in principle). As a consequence, it is held that certain truths have been superseded; for example, the definitive and complete character of the revelation of Jesus Christ, the nature of Christian faith as compared with that of belief in other religions, the inspired nature of the books of Sacred Scripture, the personal unity between the Eternal Word and Jesus of Nazareth, the unity of the economy of the Incarnate Word and the Holy Spirit, the unicity and salvific universality of the mystery of Jesus Christ, the universal salvific mediation of the Church, the inseparability — while recognizing the distinction — of the kingdom of God, the kingdom of Christ, and the Church, and the subsistence of the one Church of Christ in the Catholic Church.
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Therefore, in connection with the unicity and universality of the salvific mediation of Jesus Christ, the unicity of the Church founded by him must be firmly believed as a truth of Catholic faith. Just as there is one Christ, so there exists a single body of Christ, a single Bride of Christ: “a single Catholic and apostolic Church”.51 Furthermore, the promises of the Lord that he would not abandon his Church (cf. Mt 16:18; 28:20) and that he would guide her by his Spirit (cf. Jn 16:13) mean, according to Catholic faith, that the unicity and the unity of the Church — like everything that belongs to the Church’s integrity — will never be lacking.52
The Catholic faithful are required to profess that there is an historical continuity — rooted in the apostolic succession53 — between the Church founded by Christ and the Catholic Church: “This is the single Church of Christ... which our Saviour, after his resurrection, entrusted to Peter’s pastoral care (cf. Jn 21:17), commissioning him and the other Apostles to extend and rule her (cf. Mt 28:18ff.), erected for all ages as ‘the pillar and mainstay of the truth’ (1 Tim 3:15). This Church, constituted and organized as a society in the present world, subsists in [subsistit in] the Catholic Church, governed by the Successor of Peter and by the Bishops in communion with him”.54 With the expression subsistit in, the Second Vatican Council sought to harmonize two doctrinal statements: on the one hand, that the Church of Christ, despite the divisions which exist among Christians, continues to exist fully only in the Catholic Church, and on the other hand, that “outside of her structure, many elements can be found of sanctification and truth”,55 that is, in those Churches and ecclesial communities which are not yet in full communion with the Catholic Church.56 But with respect to these, it needs to be stated that “they derive their efficacy from the very fullness of grace and truth entrusted to the Catholic Church”.57
17. Therefore, there exists a single Church of Christ, which subsists in the Catholic Church, governed by the Successor of Peter and by the Bishops in communion with him.58 The Churches which, while not existing in perfect communion with the Catholic Church, remain united to her by means of the closest bonds, that is, by apostolic succession and a valid Eucharist, are true particular Churches.59 Therefore, the Church of Christ is present and operative also in these Churches, even though they lack full communion with the Catholic Church, since they do not accept the Catholic doctrine of the Primacy, which, according to the will of God, the Bishop of Rome objectively has and exercises over the entire Church.60
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“The Christian faithful are therefore not permitted to imagine that the Church of Christ is nothing more than a collection — divided, yet in some way one — of Churches and ecclesial communities; nor are they free to hold that today the Church of Christ nowhere really exists, and must be considered only as a goal which all Churches and ecclesial communities must strive to reach”.64 In fact, “the elements of this already-given Church exist, joined together in their fullness in the Catholic Church and, without this fullness, in the other communities”.65 “Therefore, these separated Churches and communities as such, though we believe they suffer from defects, have by no means been deprived of significance and importance in the mystery of salvation. For the spirit of Christ has not refrained from using them as means of salvation which derive their efficacy from the very fullness of grace and truth entrusted to the Catholic Church”.66