Surely you are not claiming that God was not in the habit of anointing and appointing leaders? The Old Testament is full of such appointments. And if Jesus did not appoint Peter, to whom did Jesus give the keys of the kingdom? Who has them?
"But he turned and said to Peter, Get behind me, Satan! You are a hindrance to me. For you are not setting your mind on the things of God, but on the things of man.
Rock? Yeah...a hindrance (stumbling block), not to mention when he denied the Lord three times!
So, yes... God did appoint a leader. His only begotten son. Jesus.
As for the keys? Metaphor for the apostolic authority given to ALL of the Apostles as they were to spread the gospel.
Hoss