In the New Testament the Greek word translated "new" in "new covenant" is, with one exception, kainos. It means "'new' as to form or quality, of a different nature from what is contrasted as old" (Vine's Complete Expository Dictionary of Old and New Testament Words, 1985, "New," emphasis added).
Only in Hebrews 12:24 is the different Greek word neos used for "new" in "new covenant."Neos "signifies 'new' in respect to time, that which is recent; it is used of the young, and so translated, especially the comparative degree 'younger'; accordingly what is neos may be a reproduction of the old in quality or character" (ibid., emphasis added).
Neither Greek word translated "new" suggests that every aspect of the Sinai or Old Covenant was replaced. Each only indicates that the more recent covenant has enhanced and improved the quality of the original covenant.
The New Covenant unquestionably provides a better relationship with Elohim than the relationship portrayed only symbolically in the former covenant. To ensure this better relationship, some new features have been added to the "new" (or qualitatively improved) covenant and some obsolete features have been replaced. But features common to both covenants remain unchanged and unaltered.
That new relationship is available only through Yeshua Messiah, our new High Priest and our real sacrifice for sin. Christ's death, by paying for humanity's sins, has opened the door for all who willingly repent to receive Elohim's Holy Spirit and be accepted by Elohim as His sons and daughters. As our permanent High Priest, Yeshua replaces the high priest who was merely a human descendant of Moses' brother, Aaron.
Elohim's "new" covenant also offers enormously better promises. Yet it abandons none of those spiritual principles that eternally reflect Elohim's mind and character. Those principles are explained accurately and adequately enough in the Old Testament scriptures. Yeshua and all of His apostles, including Paul, used these Scriptures as their authority for the true teachings of Elohim (Matthew 4:4; Acts 17:2; Romans 1:1-2; 2 Timothy 3:14-17).