And Catholics claim that Catholicism is the “One True Church”.
It forfeited the right to be called a church a LONG time ago. Like hundreds of years, at least.
It never was the “One True Church,” seeing is a result of progressive deformation, with accretions of distinctive Catholic teachings that - as you well know - are not manifest in the only wholly God-inspired, substantive, authoritative record of what the NT church believed (which is Scripture, in particular Acts through Revelation, which best shows how the NT church understood the gospels)
And contrary to claims of cults, the only one true church which is the body of Christ (Colossians 1:18) to which He is married, (Ephesians 5:25) being the "household of faith," (Galatians 6:10) for it uniquely only and always consists 100% of true believers, and which spiritual body of Christ is what the Spirit baptizes every believer into, (1Co. 12:13) as "living stones" in this "spiritual house," (1 Peter 2:5) while organic fellowships in which they express their faith inevitably become admixtures of wheat and tares, with Catholicism and liberal Protestantism being mostly the latter.
However, some Catholics themselves imagine a popeless mystical church, their Holy Mother Church as being The One, Holy, Catholic, and Apostolic Church which is spotless, without blemish, absolutely untouched by the unfaithfulness of laity and prelates, and modern popes of the past few decades who allowed a massive wave of debauchery.