The addressing to the angels of the seven churches is noted in verse 11. The vision is revealed to John and is to be delivered to the identified assemblies; and he was told to write the message in each case “to the angel of the church…” Why these are recorded to seven angels has always been viewed with some imposed difficulty by us groundlings. As has been noted, the word for angel may also correctly be translated as a messenger. In this case we are told that seven angels in heaven were required to post the instruction from Christ as it was to be delivered in the form of a letter or scroll, written by the hand of an Apostle of Christ. In this fashion, it has the direct sanction of both heaven and the Apostles of Christ. You might recall that heaven’s writ had by this time been given over to certain men to publish as “earthen vessels.” You should also know that not the Lord God Almighty, not the Holy Spirit, not the Christ, not their agents nor the angels have given any indication or instruction that they will ever intervene, provide or direct anything further since the writing of Revelation, as Christ had been enthroned “in Heaven” having left this earth; and things here until judgment have been concluded. That notion may seem unreasonable or unbelievable to some but should hold no difficulty to any serious reader of the Scriptures.
Therefore, the view is that the text should have the literal translation of the Greek word indicating an immortal messenger, an Angel of God, each watching the identified churches; and each vision is given first to the angel of each specifically mentioned assembly, who delivers it as addressed to the Apostle John to be written and carried to each named assembly. God is guaranteeing delivery through the angels to those churches by the Apostle of Christ. The line of authority was set. None of that line exists here since.
There were more than seven churches in Asia, so the writing signifies an explicit purpose. These personal letters are specific to the addressed groups, and by many are conceded to stand as types for others; and are an example of the use of type and anti-type in prophesy. What in the New Testament does not have that purpose? While the seven churches are the type, all churches, both then and now, which fit into these patterns are anti-types. With that noted, I rather suspect that the churches are being singularly and specifically addressed for the exact reasons stated. Verse 12 describes Christ among the lampstands, or as intended, Christ among the churches, noting that the Lord is always watchful of His assemblies. He gave his life for them. For verse 16 see Hebrews 4:12.