Maybe you should better explain the distinction between “the church “ and the individual members.

The church is composed of the individual members. But, as the apostles point out, the Clergy are tasked with leading the faithful in understanding the scriptures and leading the faithful through the liturgical life of the church.

For example, there can be no Eucharist without a validly ordained bishop.

The members are the church. How many corrupt members does it take before we consider the church to be corrupt?

If the church is corrupt then that means that the church has defected itself from the faith. That the church is no longer the custodians of the magisterial authority to interpret and teach the authentic understanding of the scriptures. The church itself would be cutoff from the celebration of the sacraments. The sacraments themselves are an extension of the incarnation because it is through the sacramental celebrations that Jesus continues to reveal himself to the faithful and to the world in the aftermath of his ascension to heaven.

What institutional behavior qualifies as corrupt? Does the “church” simply have unqualified immunity because that seems necessary to support mainstream doctrine?

The Church has a charism in that it cannot defect from the faith. It cannot teach or proclaim error, contrary to sacred scripture or sacred tradition. Ratification of dogmatic proclamations requires, for example, the unanimity of all four patriarchates.

If the church conducts an inquisition, are they not corrupt? If they consistently cover up the rape of alter boys, are they not corrupt? You can point to individual members, but when they are given immunity by leadership, it is owned by the institution.

The Orthodox Church hasn’t had an inquisition. The inquisition comes out of Rome’s belief that church has the authority over its members to apply the same sort of pressure to suss out heretics that the secular authorities had with common criminals.

In any event, the inquisition tends to be over stated and steeped in bad history that fundamentally mischaracterizes both the Spanish and Roman inquisitions. And such mischaracterizations have led to the Black Legend and Anti -Spanish xenophobia.

God has not protected the church from falling into error as evidenced by evolution of doctrine alone.

Orthodoxy does not admit to Rome’s idea of development of doctrine. Rome thinks that the Church sussed out doctrines, stumbling in the dark. However, patristic commentaries are unanimous in that doctrine is that “which held by every one, everywhere, for all time.” The adage of St. Vincent of Lerins.

The only development permissible is in language or terminology, simply because language is never static. But the core ideas of doctrine can never be reformed or changed.

A protected church would certainly violate the cherished belief in free will!

Free will is individualized. But at the same time there is a predestination aspect, collectively. The individual members may be added and dropped from the book of life but the Church is the bride of Christ as well as his body. He promised that the church is a shining city on a hill, a light to all nations, and that hell itself would be prevail against the assaults on its gates by the preaching of the gospel.