Just as there were blameless, righteous people at peace with God under the law of Moses before the revelation of the gospel of Jesus (Luke 1:6), there are righteous people at peace with God who were under the law of nature and conscience while in this life.
Blameless doesn't mean they never sinned. It means they were aware of their sin through whatever avenue of revelation that was available to them and they found forgiveness and peace with God and turned away from that unrighteousness. Just because they didn't have the specific knowledge of the blood and body of Christ through which God can forgive people doesn't mean they could not be forgiven if they turned to God in sorrow and repentance (i.e. King David).
The unsaved dont know God, they worship demons.
To know God and His Son Christ is eternal life. To not know them is eternal death. Christ calls such people, the ones He does not know, workers of iniquity (evil).
1 John 5:2
By this we know that we love the children of God, when we love God, and keep his commandments.
1 John 5:13
These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.
1 John 5:18
We know that whosoever is born of God sinneth not; but he that is begotten of God keepeth himself, and that wicked one toucheth him not.
1 John 5:19
And we know that we are of God, and the whole world lieth in wickedness.
1 John 5:20
And we know that the Son of God is come, and hath given us an understanding, that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life.
John 17
King James Version
17 These words spake Jesus, and lifted up his eyes to heaven, and said, Father, the hour is come; glorify thy Son, that thy Son also may glorify thee:
2 As thou hast given him power over all flesh, that he should give eternal life to as many as thou hast given him.
3
And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.
Jesus does not know as in have a relationship with those who do not believe in Him, but they claimed to be doing the works of God, but they were liars.
Matthew 7:22-23
King James Version
22 Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.