In “The Christian Meaning of Enlightenment”, Franciscan priest Richard Rohr gives a Catholic perspective on western faith and the loss of its non-dual perspective. He refers to his teaching as a “Franciscan alternative orthodoxy.”
He makes many excellent points though I’d disagree experiencing a “unitive” experience once will do the job. It may certainly change one’s perspective. But actual non-duality is not an experience. It is a lived reality with the resulting seeing he speaks of.
For example, he spoke about us not having the software to see – right after making a statement about the exclusive uniqueness of Christianity that was both dualistic and false.
I’d also suggest he misses why it was lost. When the means to unite with the divine is lost, so too is the seeing. Then things degrade into concepts, then beliefs, then dogma.
I’d agree you should follow the golden thread. But don’t hold on to it. That’s the dualistic ego trying to control. Allow it to unfold.