The proclamation of the heavenly host emphasizes God’s initiative in bringing this good news of peace “among those with whom he is pleased.” In other words, God will bestow this peace however He is pleased to do so, on whomever He wills. This is not to be understood in the sense that His peace will come to those who have something within them that pleases God, but in the sense that God does whatever He pleases. He will bestow this blessing according to His good pleasure.
God reveals Himself to whomever He wills. It is according to His good pleasure that He bestows this blessing, and there’s nothing we can do to earn a place in that audience. God reveals Himself in some of the most unlikely ways, to some of the most unlikely individuals (like shepherds!). It just goes to show that He is absolutely free and sovereign in the salvation of sinners. And this means that He gets all the glory. “Glory to God in the highest” as He sovereignly reveals Himself and draws sinners (His enemies) into a peaceful relationship with Him, a saving relationship.