I do not I would agree. Christ deposited unity in the Church [Cf. John 17:21]. That unity subsists in the Church, thus without it "Church" no longer exists. To say the words "I believe" does not make a member part of the Body of Christ, unless that "I believe" is subsistence in the unity of the Body of Christ.
In fact, "in this one and only Church of God from its very beginnings there arose certain rifts, which the Apostle strongly censures as damnable. But in subsequent centuries much more serious dissensions appeared and large communities became separated from full communion with the Catholic Church - for which, often enough, men of both sides were to blame." The ruptures that wound the unity of Christ's Body - here we must distinguish heresy, apostasy, and schism - do not occur without human sin:
Where there are sins, there are also divisions, schisms, heresies, and disputes. Where there is virtue, however, there also are harmony and unity, from which arise the one heart and one soul of all believers.[Origen, Hom. in Ezech. 9,1] [CCC 817]
Else, one is insisting on being part of the Body while residing outside the Body. Somehow that doesn't seem to work, especially if one is to drink of the same root.
Consequently I cannot hold to being a part of, while not part of. Yes, catholic means universal, but it doesn't mean universality.
JosephT