...it is wholly insufficient merely to proclaim either to ourselves or to the wider world that "everything is holy now" without, at the same time, living ourselves and offering to others a coherent religious practice that allows such an insight to be shown by us in our words and deeds and, therefore, passed on to those who chose to follow us.
I've been thinking along these lines for a while now. I want to ground my life and spirituality in a coherent understanding of reality. This understanding is bound to grow and evolve, possibly in response to experience and ritual and spiritual practice; but it is good to have a theological or theoretical basis for one's practice. (Note that by 'theological' I don't necessarily mean having to do with deities, and I certainly don't mean anything dogmatic.) If you don't have a theoretical underpinning for your practice, you become known as the religion where you can believe what you like (instead of a religion that is engaging in a search for the truth, whatever that turns out to be).
It's not enough to say that all paths point to the same underlying mystery - one needs criteria to ascertain which path gets there without pitfalls along the way. One needs to be able to explain how spiritual paths that look wildly different on the surface actually do point to the same underlying mystery. I think that the common features of different paths can be found by looking at how they relate to the processes of transformation within the human psyche, which seem to be consistent at least within cultures, and probably across cultures too. However, one needs to make this comparison without implying that the experience is merely psychological; without reducing the rich variety of colours of different traditions to a sort of sludgy mystical fog; and whilst respecting the particularities (historical, cultural and spiritual) of different traditions.
With that caveat in mind, what are the common features of different paths? They have been described in various ways in various traditions (Alchemy, Kabbalah, Wicca, the mystics' journey into the interior castle, Jacob's Ladder in Freemasonry, Jung's description of the individuation process, Campbell's Hero Journey, Lewis Rambo's stages of conversion).
Common features of all these descriptions of the spiritual journey are the sense of descent into one's inner world, which is also connected with the vast interior space of the collective unconscious or the Divine; the realisation that one is inwardly connected with everyone else; the experience of encountering the Void (possibly including self-emptying, or at least the setting aside of the ego); then entering into a larger consciousness (sometimes described as theosis). These experiences are probably more accessible if one takes the view that the Divine is accessible through inward contemplation; that the whole of reality is suffused with the Divine presence; that we ourselves carry sparks of the Divine. But sometimes people go through these processes of inner transformation in spite of having very different ideas of the nature of reality - which is what suggests to me that they are intrinsic to the functioning of the human psyche and its relationship to the universe.
Just as it is possible to have a deeper insight into one's own language and culture if one is conversant with another language and culture (preferably having been immersed in that other culture to some extent), so also it is possible to have a deeper engagement with one's own religious tradition by engaging with other spiritual traditions. I did not understand what Jesus was saying until I had compared his ideas with those of Sufism and Taoism. I am immersed in the symbol system of Wicca (and have been for twenty years now), and having travelled on my spiritual journey through its particular highways and byways, I can appreciate the shape of other spiritual journeys, including that of Christian mysticism - but I could not have travelled by that route because I was encumbered with the baggage of an evangelical Christian background. I had to set Christianity to one side for a long time before I could look at it afresh and see it differently.
You have to travel by one particular route in order to experience the journey fully - but it's good to find out about other journeys and compare their particular scenery with that of your own. If you don't have a concept of journeys and maps, you might never even set out on the journey; and if you don't get tips from other travellers, you might head off in the wrong direction entirely.