A society is made up of laws and generally agreed upon assertions and conventions. A constitution is a formalization of those things.

We enshrine and worship our Constitution as if it were a perfect document, but it is far from that.

Enshrining implies stasis. A good constitution is one that changes over time to better suit the circumstances. One of the great flaws of the current USA Constitution is that its mechanism for change, Article V, is weak to the point of dysfunction. Therefore, the primary reason that our Constitution isn't very good is because its mechanism for change is not very good.