Read carefully. I did not say that the Church was open only to the Apostles. I said that the Church was founded on the Apostles. It was to the Twelve that Jesus gave the command to "do this in memory of me". It was to the Twelve that he gave power to bind and loose sin ("whose sins you forgive, they are forgiven"). It was to the Apostles that Jesus gave the Great Commission. Was Paul one of the Twelve?
It is through the transmission of an uninterrupted Apostolic succession within the Church that we are able to receive Communion.
From whom did Paul receive his commission?
Was Paul one of the Twelve? The Great Commission refers to Matt. 28. Paul wasn't around.
And the eleven disciples went into Galilee, unto the mountain where Jesus had appointed them.