The OT is more than the law. From it we also get the following:
Therefore thus says the Lord God, "Behold I am laying in Zion for a foundation, a stone, a tested stone, a precious cornerstone, of a sure foundation; he who believes will not be in haste." And I will make justice the line, and righteousness the plumbline.
Isaiah 28
Ironic, isn't it? You claim we don't need the OT to understand the Lord, and yet you use its language to describe him.
Which then begs the question; did God make a mistake in giving the law to the Israelites, or did the Israelites make a mistake in interpreting how to use that law. In other words, there is nothing wrong with the law itself. Paul followed it, Christ followed it, the disciples followed it. The law does not lead people astray, following the letter of the law while forgetting the heart of the law is what leads people astray.
Love is at the heart of our faith. If a person can love God with all their heart, soul, mind and strength and follow the law, then good for them. If they can do all of that, but not follow the law, then they have lost nothing. It is love that matters.