So is the problem rationalism, or fundamentalism?

It seems you might be throwing the baby out with the bathwater.

Considering the real mystery is this sentient awareness we all seem possessed by, rather than the many perceptions it observes and concepts it contemplates, would a spiritual absolute be an ideal of wisdom and judgement from which we fell, or the essence of sentience from which we rise?

What would be the consequences of a culture founded on the principle of assuming the ideal to be absolute? Logically it would be an inclination to all variety of fundamentalisms.

Remember that democracy and republicanism originated in pantheistic cultures and Rome adopted and co-opted Christianity to be the state religion as the Empire solidified and remnants of the Republic faded. When the West went back to more broad based systems of governance, it required the separation of church and state, since the effective function of monotheism was to validate monarchy. The Big Guy rules. "Divine right of kings."

In nature, synchronization is centripetal, while harmonization is centrifugal, so nodes and networks, organisms and ecosystems.

Good and bad are not some cosmic conflict between righteousness and evil, but the basic biological binary of beneficial and detrimental. The 1/0 of sentience.

If we assume good to be an ideal, than everything not white is black.

We developed the capacity to reason, because it is necessary for survival, even if the powers that be don't always approve of where it leads.