Though the Biblical Law can inform culture, it is a moral code first and foremost. People who supplant this moral code with a culture miss the point of why Jesus had a
problem with the Pharisees who were preaching the jewish culture of the time over God's Law. It's not about becoming jewish, it's about obedience to God. Failure to make this distinction will only result in condemnation. People can/will hold to their respective cultures, but what a professing Christian does when there is a conflict between the Law and their culture will reveal where their values/beliefs truly lie.
That said, if all one is looking for is a moral framework for society and don't care much for the idea of God then moral solidarity becomes the goal. Either way, heretics in terms of God's Law or society's laws tend not to fare well and are often convinced of their own superiority, sometimes via a martyr complex (persecution = validation).
Also, God's Law states that there was
nothing inherently special about the Hebrew people and the fact that the Lord would go on to punish them throughout the ages (even in their own texts) is further proof of this. The Biblical feasts are reminders of God's goodness/provision/power and not about how "special" the Hebrews were. The feasts are, in summation; remember the Lord and what He has done. I'll stop here.