Let’s start with the basics: Is there really angelic activity in a near but unseen realm? Yes. I believe angels are active in our world today — more than we realize. They were active in biblical times and there’s no indication to suggest their activity has ceased.
Angels populate the Bible in vast numbers, and they were prominent in the book of Acts as the apostles began taking the Gospel to the world. Why should they cease their work with the writing of the last book of the New Testament?