Paul has been delegated by God to preach. He actively chose Paul according to His eternal purpose. God used Paul to deliver His message to the consecrated followers of Jesus, those who had believed and were trustworthy and true to the cause of Christ. Most translations attribute this letter as addressed to the church at Ephesus, but many important manuscripts do not include ‘at Ephesus’, so it seems apparent that the letter was intended for a much wider distribution. Since it is included in the Holy Scriptures that would include the church of today.
If I consider myself to be a faithful follower of Christ and God has chosen Paul to speak to the church across untold generations it would behoove me to pay careful attention to what he has written.