It was the Word who said this. The Word became a Man named Jesus Christ. This Man brought in a Covenant which was not according to the covenant He, as the Word, made with them, but He, as Jesus Christ, brought in a different Covenant where the Law is not on tablets of stone but on the heart, where circumcision is not of the foreskin, but of the heart, where being lead is not by another man, but by the Man Himself.
The Word said that He will bring in a Covenant which is different, and as the Word incarnated, He certainly did. We now walk spiritually and not physically.
Different Covenant, same Laws. The problem was never with the Laws, it was with the people...
Heb 8:7 For if that first covenant had been faultless, then should no place have been sought for the second.
Heb 8:8
For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah:
Deu 5:29 O that there were such an heart in them, that they would fear me, and keep all my commandments always, that it might be well with them, and with their children for ever!
The Laws were perfect...
Psa 19:7
The law of the LORD is perfect, converting the soul: the testimony of the LORD is sure, making wise the simple.
The problem is with people...
Rom 8:7 Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be.
The carnal mind is at enmity with God and cannot keep His Laws.