The Old Covenant was given to point the Way to Christ. It was mainly about a ritualistic system of atonement for the sins of the people, and to direct them into following God's Ways, while all pointing to Christ Who was to come. God's grace played a part in it also, but through ritualistic means of animal sacrifices and offerrings and a fleshy priesthood. Within it, God gave His law, which none could be perfect in keeping, again pointing to the need for a better Covenant through Christ Jesus.
Many of the laws God gave with the Old Covenant still stand today for civil and moral purposes, and health purposes. But Salvation of one's soul is only by The New Covenant through Christ's Blood shed on the cross. We no longer need ritual sacrifices, nor go through any flesh priest for atonement of sin, but through Christ Jesus only.
It's important to separate the Old Covenant ritual and religious worship from many of God's laws that still stand today for Christianity. Though God's law is not The New Covenant, it's still to be a factor among God's people to keep order, for as Apostle Paul said in 1 Tim.1-3, "...that the law is not made for a righteous man, but for the lawless and disobedient, for the ungodly and sinners, for unholy and profane, for murderers of fathers and murderers of mothers, for manslayers, For whoremongers, for them that defile themselves with mankind, for menstealers, for liars, for perjured persons, and if there be any other thing that is contrary to sound doctrine; According to the glorious gospel of the blessed God, which was committed to my trust."