The angel does not expound on what he says to fully explain everything he says.
Not an expository preaching of the whole gospel and counsel of God
He says three things
Then the angel said to them,
1.“Do not be afraid, for behold, I bring you good tidings of great joy which will be to all people.
2. For there is born to you this day in the city of David a Savior, who is Christ the Lord.
3 And this
will be the sign to you: You will find a Babe wrapped in swaddling cloths, lying in a [
d]manger.”
13 And suddenly there was with the angel a multitude of the heavenly host praising God and saying:
14 “Glory to God in the highest,
And on earth peace, goodwill[
e] toward men!”
Then they leave
This is an announcement coming from heaven regarding the birth of Christ, it is not the gospel of Christ in which many secrets are revealed.
Of course it is marvelous, wonderful, and would have been amazing to see.