Someday, in God's time, creation will be complete. We humans have no idea what that means, but we like to imagine a world of justice and peae. In the meantime, remember, at Pentecost God sent the Holy Spirit into the world. Plus, we all receive the Holy Spirit at our Baptism, which means that Jesus has already come to live within each of us. Jesus came to take away the punishment for sin, but he didn't take away sin itself.
Sin still exists.
God allows us to make choices, and not all of our choices are to obey God above all else. That's what free will is. When all of our disobedient choices get together, they contribute to the total picture of sin in the world, from the beginning of time. Some people call it systemic evil. Racism is a systemic evil, and so are sexism and world hunger.