You don't need a "there is no God" experiment, at least if the only god that's actually on your hypothesis space is the abrahamic one

All other hypothesis win over an omnipotent god. That model has infinite complexity and allows every law of nature to be broken due to infinite power being an intrinsic part of that entity. You need infinite evidence to even start considering it over every other non infinitely complex hypothesis that doesn't imply everything we know about physics being wrong

And they don't even give it a good excuse unlike, for example, living in a simulation

As for the other gods... Well, whoever thinks they are likely will have to give at least some epistemologically valid argument for them. Which for the most part they don't, although I'm willing to be convinced otherwise

People require more evidence to believe a bench is wet than they do to believe in most religions. I'll convert once there's good arguments to convert, until then I'll chuck gods in the generic set of "unlikely stuff that needs more reason to be considered", which is quite the big set

I think for most world religions, belief that spiritualism is isolated as a purely metaphysical affair is a minority, nearly fringe belief. If you isolate spiritualism to the purely philosophical realm then religion loses its potency, and Richard Dawkins will metaphorically laugh as he places some pasta god next to the sacred.

Spiritualism is as much about this world as it is about concepts of afterlife.

I'm not sure it is. It isn't for me. I don't really believe there is no god, i am however certain that I am more likely to get the wrong one than not (statistically). Thus, rather than taking a belief and moral system from a book, i choose to act as if I don't have one and act following a consequentialism that suits me.

But honestly, 99% of the time, i just don't care.

Isn't that experiment currently running?