The promises were conditional. Israel, like all of mankind, falls short of the glory of God. The New Covenant is also conditional (like all of the others). He wants us to fully commit to Him.
True, all men have sinned and fall short of the glory of God. No one can be perfect or work their way into Heaven. That’s why we need a Savior.
Would you agree that there are Hebrews who preceded Christ’s first coming that are with God? Just read Hebrews 11.
The new covenant is conditional but the only condition is belief in the atoning sacrifice of Christ for the forgiveness of sins and His imputed righteousness for salvation.