Except that Jesus himself said that all the stuff in the Old Testament is still relevant, see Matthew 5:17-19:
Do not think that I have come to abolish the Law or the Prophets. I have not come to abolish, but to fulfill. 18 For truly I say to you, until heaven and earth pass away, not one dot or one mark will pass from the law until all be fulfilled. 19 Whoever, therefore, breaks one of the least of these commandments and teaches others to do likewise shall be called the least in the kingdom of heaven. But whoever does and teaches them shall be called great in the kingdom of heaven.
Matthew 23:
Then Jesus said to the crowds and to his disciples: “The teachers of the law and the Pharisees sit in Moses’ seat. 3 So you must be careful to do everything they tell you.
Of course it's relevant. Jesus himself quotes last 5 Commandments: Mt 19:16-19