“The question w/in Christendom that has been argued for centuries (and w/in FR) has been: “who/what is Christ’s church?””
That was not Yeshua’s conversation. The conversation with the disciples in the scripture is about who do people say Yeshua is. The correct answer was given by Peter, and Yeshua says THAT ANSWER, that Yeshua is Christ, is the foundation of His Church. Not Peter.
It's clear in Matt 16:18 that Jesus said the gates of hell will not prevail against His church! You are conflating Jesus' clear reference to His "church" with Peter's role. .
No one is arguing that Jesus is the foundation of His church! However, there has been and continues to be argument as to who/what constitutes Jesus' church.