“So if an angel can be sent by God to us, with a message, why can the reverse not happen?”
You are not God, as it turns out.
“Why can we not send the angel to God with a message or request, from us?”
Angels are messengers of God. They are not your messengers.
Why yes they are!
And another angel came, and stood before the altar, having a golden censer; and there was given to him much incense, that he should offer of the prayers of all saints upon the golden altar, which is before the throne of God. [4] And the smoke of the incense of the prayers of the saints ascended up before God from the hand of the angel.
Revelation 8: 3-4