19 For in him all the fullness of God was pleased to dwell, 20 and through him God was pleased to reconcile to himself all things, whether on earth or in heaven, by making peace through the blood of his cross.
God reconciling all things through the blood is all through the OT as well. All things are reconciled by His death on the cross, so that without the cross killing Him, the blood and the water signifying His death on the cross, for out of Him came both water and blood proving His death, there would be no forgiveness and the OT saints were not completely perfected, they had to wait in paradise in hell till Christ came as their savior and deliverer.
1 John 5:6
This is He that came by
water and blood, even Jesus Christ; not by water only, but by
water and blood. And it is the Spirit that beareth witness, because the Spirit is truth.
1 John 5:8
And there are three that bear witness on earth: the Spirit, and the water, and the blood; and these three agree in one.
Hebrews 9:22
And by the law almost all things are purged with
blood, and without
shedding of blood there is no remission.
The OT sacrifices were only for the people of God, not the world, not for those who had no covenantal relationship with God, not for 'heathen' not for the profane, not for the other nations.
God in the NT has included the gentiles to be a part of His kingdom, key to this is in v14 where it is God who has chosen out from among the gentiles a people for His name, but not all of the gentiles since not all gentiles are saved, but only those God has taken for Himself, only they have the atonement of their sins.
Acts 15:13-1721st Century King James Version (KJ21)
13 And after they had held their peace, James answered, saying, “Men and brethren, hearken unto me.
14 Simon hath declared how God at the first visited the Gentiles to take out from them a people for His name.
15 And to this agree the words of the Prophets, as it is written:
16 ‘After this I will return, and will build again the tabernacle of David, which has fallen down. And I will build again the ruins thereof, and I will set it up,
17 that the residue of men might seek after the Lord, and all the Gentiles upon whom My name is called, saith the Lord who doeth all these things.’