The Church is also the living Body of Christ without which Sacred Scripture and Sacred Tradition would cease to exist. God declares that His Word shall never pass away, but perhaps the chief method by which He ensures the fulfillment of that prophecy is by the parallel fulfillment of the prophecy that the gates of hades shall never prevail against the Church. Hades is the abode of the dead, so this, among other things, means that the Church shall never die. And if the Church can neither die nor be destroyed, then this same One, Holy, Catholic, and Apostolic Church shall always be alive in the world to perpetuate the preaching of the Written Word of God (Scripture) and the teaching of the Spoken Word of God (Tradition), both of which flow from the very Heart of the Son, who is the Living Word of God (and thus also flow from the heart of the Church).
I know you’re not saying that the Church has no purpose; you’re just trying to understand what its purpose is. So consider this: if the Church, which is Christ’s Body, had no purpose, then Christ Himself, who is perfectly One with His Body, must likewise be understood to have no purpose, since it is by the personal charism of Christ the King that His Visible Body, the Church, continues His ministry of preaching, teaching, and administering the Sacraments. He and His Church are intimately and integrally linked for all eternity. The purpose of the Church, which is the people of God, is to be Christ to the world. So, since His purpose is the most paramount purpose ever taken up throughout all time and space, then so is that of His Church. Tradition and Scripture are of absolutely unfathomable importance - amen! - but without the Church to faithfully pass them on to each successive generation, how would we know anything of them? We’re already seeing, through the machinations of those who have completely cut themselves off both from the Catholic Church and thus from the Sacred Tradition that flows from It, the utter degradation and dismantling of Sacred Scripture by a group that dares call itself by Christ’s own name: “The Jesus Seminar”. Without the Church to safeguard and faithfully echo the Truth, there would be none left…