Clearly, the righteousness of Christ, the Holy Spirit, was not absent in Jesus. But Jesus Christ came to die; that was his purpose. Only through death and resurrection could God's righteousness become our righteousness! The Spirit of Christ could not be sent from heaven until after Jesus Christ had been resurrected and exalted.
'For a testament is of force after men are dead: otherwise it is of no strength at all while the testator liveth.' [Hebrews 9:17]
Jesus Christ did not come to teach anything that was not already in the law. He came to offer HIMSELF as the fulfilment of the law, so that we might have life.
IMO, Jesus Christ wants us to live by faith in Him!
'For this is the covenant that I will make with the house of Israel after those days, saith the Lord: I will put my laws into their mind, and write them on their hearts: and I will be to them a God, and they shall be to me a people:
And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest.
For I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more.' [Hebrews 8:10-12]
There is only one way, IMO, to have the law written on your heart, and that's to have the Holy Spirit indwelling. The only way to get the Holy Spirit is through repentance and faith in Jesus Christ.