The New Covenant is better because it does not require the impossible, but rather provides it. "I will put my Laws into their minds, and write them on their hearts." The whole rest of the paragraph shows that what is promised here is a change in nature, a change in the heart. Whereas formerly we hated th law and saw it as foreign, now we shall love the laws of God and be drawn to Him and them by our very hearts.
This is the only way to God. He must change us. He must change me. I despair of my old selfish nature which repeatedly disappoints me. If I am ever to have fellowship with God, it will be because he has reached in and actually, actively changed my heart and the kinds of things I love. I cannot make myself love the things I do not love. But God can and does. This is the new birth and the new nature that is spoke of elsewhere in scripture.