The Mosaic Covenant was meant, in part, to condemn everyone of their sin and to help them realize that they fall far short of God's righteous standards. Additionally, the Mosaic Covenant pointed to Jesus and his redemptive work through types and shadows.
Judaizers promote the observance of obsolete commandments of the Mosaic Covenant as continuing moral requirements especially some of the shadows and types. Some of them even think non-observers are unsaved.
I used to be one of them as an Armstrongite. Thank God that he liberated me from the nonsense that Judaizers teach.
I recommend reading "Freedom in Christ" by Meno Kalisher to clarify your thinking on this topic. Judaizers can put up a pretty convincing argument that can entangle you in nonsense if you're not careful.
Freedom in Christ | Friends of Israel
The Mosaic Covenant did reveal God's holiness in a faint sort of way, because there was a "law" underlying the Mosaic Covenant. And, a spiritual man can read the Mosaic Covenant and discern some underlying moral and spiritual principles. However, the Mosaic Covenant (and law) is not in effect anymore, and this is clear. Read Acts 15, Ephesians 2:13-15, Romans 7:1-7, Hebrews 8-9, Galatians 3-4 and II Corinthians.
The purpose of the Law is to serve a ministry of condemnation. It condemns us individually so that we know our sin. This should drive us to seek grace and forgiveness through the atoning sacrifice of Jesus Christ, and the gift of righteousness that this reconciliation brings. We are given a new nature that wants to please and obey God as a result...particularly important is displaying sacrificial love toward others.
Judaizers are continually focused on things like claiming that physical circumcision, dietary or calendar observances are required, and in judging non-observers. They rarely focus on elements like sacrificial love toward others. That is why I utterly repudiate the teachings of my past and won't fellowship with Judaizers.
Please note that I'm not including individuals who observe Sabbath and festivals because they are meaningful shadows and types. In fact, I'd likely attend such a congregation IF it was Christ-centered and not judgmental, but there is no such group around here. Most of them are nutty conspiracy theorists who hold a National Enquirer view of Christianity and church history, depending on shoddy works like Alexander Hislop's Two Babylons to make their claims.
Beware if you are considering fellowshipping with some of these types; many of them deny the full deity of Christ, the writings of the apostle Paul, and the Trinity doctrine. The dividing line for me is if any group claims these observes are requirements, conditions, or necessary fruit of salvation, then they are in violation of the admonition of Galatians, and Paul declared Judaizing heretics anathema in Galatians 1:6-7.