The key to this parable (in my opinion) is the revelation that the Kingdom of God, and God’s Salvation are not the same concept. The latter is guaranteed through Grace for all, the former is not a guarantee at all, and not all will be able to participate in its coming on Earth as it is in Heaven. Worse, some won’t want to participate.
21. “No one sews a piece of unshrunk cloth on an old cloak; otherwise, the patch pulls away from it, the new from the old, and a worse tear is made.
22. And no one puts new wine into old wineskins; otherwise, the wine will burst the skins, and the wine is lost, and so are the skins; but one puts new wine into fresh wineskins.”
Do you not know that friendship with the world is enmity with God? Therefore whoever wishes to be a friend of the world becomes an enemy of God. – James 4:4