I'd say the best of religion should still be supported by treating it as art. You can form a fan club around your interpretations and debates pertaining to the four gospels, for instance, a club that would be comparable to a Star Trek club or a book club. I have no problem with the celebration of art, and religions begin as cultish art.

Artists could work as defenders of an institution, but then they'd be propagandists. They'd have sold out, and their messages would be tainted by politics and economics. Now, some propaganda may be more worthy than other types, depending on the institution it promotes.

I take the point about whether human progress is natural to be largely semantic. You can think of what I like to call our "artificial refuges from the wild" as yet more natural developments that negate or complicate some preexisting natural patterns. Black holes are in some sense natural too, even as they swallow spacetime. But I'd rather emphasize the implicit anti-natural stance that motivates that existential revolt. This, though, would be a dispute about labels. What's indisputable, I think, is the trajectory of history in the big picture.

You seem to be interpreting my views as though they're implicitly scientistic or opposed to culture as such. On the contrary, I support secular humanistic culture (although I critique its downside too, such as its decline in woke decadence or infantilizing consumerism). The problem with developing a worthy religious side of this humanism is one of scaling. How to turn a cult into an organized religion for the masses without tainting the culture's artistic merits with political and economic incentives? Powerful institutions tend to corrupt their leaders, so the mission goes sideways.