I am a current practitioner of something that might, for all practical purposes, meet that description, but I don't say it that way. Instead of being on a theism/agnosticism polarity, I'd say it's on a literalism/metaphoricalism polarity. So, as nutty as it might sound, it's sort of an atheistic theism. That is to say that God is still there, just as always, but is understood to be a metaphor rather than a literal person.

In this view God is a personification of the totality of reality. The cross represents the horrifying prospect of being separated from ego-identity. Salvation is that eventual liberation from ego-identity. Heaven is the experience of living on the other side of that transformation. Life after death is not life after death of the body, but life after death of ego-identity, etc., etc.

I really suspect this is the original intent of the scripture. When you start studying it it's pretty amazing how much starts making sense that made no damn sense at all when taken literally. It's not hard to understand that a majority might have taken it literally before that prospect was diminished by science, but I think it was always a story about cognitive development, written long before such a clinical description was possible. Advanced cognitive development itself, however, has been possible for thousands of years... for those who could understand the esoteric meanings. This pattern can be seen just as easily in other religions as well. They were all trying to describe human psychology at a time when there was no way to understand it other than by metaphor.

One can certainly cherry pick Christian tropes and symbols in an infinite number of ways.

I do not see humanistic sentiments, good morals and ethics, sound and defensible philosophy etc. to have any dependency on theism generally or on Christianity specifically. I agree with you however that religion has historically delivered on community, belonging and refuge and is skilled in the use of ritual to that end. I think one walks a fine line there however because the very thing that allows a community to coalesce (common beliefs and rituals) can easily become the very thing that allows others to be excluded from that very community, for no better reason than failure to conform. As the beliefs become less dogmatic and exclusive, the community becomes more accepting and inclusive, but also loses some of the impetus to coalesce.

My personal experience has been that liberal Christian and post-Christian groups with loosely-held religious beliefs tend to acquire rigidly held views in other areas (such as politics) and become cliquish and controlling around those rather than around dogma. Meanwhile areligious groups have too little cohesion, and achieving any sort of cooperation becomes an exercise in herding cats.

I have not found an answer to this conundrum. But since my social needs are quite modest, I have to admit that I haven't been very motivated to beat the bushes, either.