Hi, Graham. I agree with certain values of secular humanism, such as freedom of speech, but I don't consider myself optimistic enough to idolize human nature. The fact that our progress may be wrecking the planet's ability to support life indicates we shouldn't necessarily be given such free rein.
So I tend to criticize both organized religions and secular alternatives to them. I'm an atheist with respect to monotheistic and anthropocentric religions and to exoteric, literalistic readings of myths. I'm a philosophical naturalist, but also a kind of pantheist, combining some ideas of Schopenhauer, Nietzsche, and Lovecraft's cosmicism. Nature is a force of inhuman, monstrous, living-dead self-creativity. That's the true divine power, the absurdity and indifference of which spur us to compete with it out of disgust and terror.
So I'm more like an "old" atheist than a "new" one. See, for example, my latest article, Scientism and the Downfall of New Atheism, where I point out how Eastern religions are superior to Western ones, because the former are more straightforwardly anti-natural and pessimistic. I've got another article coming out soon on atheism, which goes further into the problems with our secular values.
I suppose I'm kind of a philosophical mystic but with a tragic, largely jaded perspective and without much of a home in any religion I know of. (I've got problems with the Eastern religions too, which I've written about.)
I've written specifically about how I think existentialism should replace spirituality. So I'd call myself existential (striving for authenticity and integrity) rather than spiritual.
I'm looking forward to reading your response.