“Therefore, if anyone is in Christ, the new creation has come: The old has gone, the new is here!” 2 Corinthians 5:17 NIV
God has written in our hearts the word. Previously, the Word had been rules written on paper, clay tablets or stone. The written rules were not sufficient guidance, people still sinned. And even now, with the Word inscribed in our hearts, we sin. But we have this tremendous advantage. We have knowledge of our sin, and we can repent, and turn back to God. We can fail, and yet our failure can be washed clean.
People make mistakes and choices which go south. But God can still work with mistakes, and make them good. Bad preachers can still win converts. That does not mean we should do bad or to not care. Our fruit comes from the seed God has given us, but we must tend to it, to let it grow. Because those without fruit will be pruned from the tree of life.