Does the fact that the old covenant is the old covenant mean that the new covenant was “plan b”? The answer is no. God did not make a mistake with the old covenant. This article looks at the relation of the old covenant to the new covenant (the relationship between the Old Testament and the New Testament). The author also discusses Hebrews 8:6-10, Galatians 3:24-25, old covenant and Jesus Christ, and continuity and discontinuity in the covenant.
Source: Ligonier Ministries, 2004. 3 pages.