There's a vast gulf between useless and essential. For example, a church building is not essential. We could still function as a church without a building, and meet in a park, a rented space, and/or from home to home. We could still be a viable and biblical church. Yet while a church building is not essential, it is certainly not useless. We find daily benefit from having a church building to host events, meet for prayer, and most of all gather for worship on Sundays. As we will see in Romans, the Old Covenant law of God is the same way. The law is not essential for salvation, which Paul establishes in Romans 2. Circumcision and having the law is not essential for salvation. I have said before that giving the law to someone drowning in sin only buries them further. They don't need more law, but the gospel of forgiveness for salvation. Does that mean the law is useless? No - there is a vast difference between essential and useless. What then is the law good for? First, the law is useful to convict people of sin. It shows how far short we fall of God's standard, and shows us our need for Christ. Second, the law is good for the good of the world and cultural ethics. It shows us what God's priorities are and how we might order our world in light of those priorities (for example, the law shows us how God values human life). Third, the law is useful as a moral guide for God's people. While it may not save us, it does show us how saved people ought to live, and what kind of life is pleasing to God. Theologians have summarized these aspects as the "threefold use of the law." I find this to be a fairly helpful approach to differentiating between what is necessary for salvation, and what is helpful for living a life pleasing to God, as we seek to follow His ways in our world. In this, the law has much to say, and all God's word is proven to be profitable.