@jeeprs,
I acknowledge that Heidegger distanced himself from Sartre. I still see a moralism at the root of most of what gets called existentialism.
Spengler called Nietzsche a socialist, because he cared about his neighbor's values. Nietzsche (who I love despite his absurdities) whined about the decadence of man, for instance. So the great immoralist is still a moralist. He just wants folks to be more noble. At other times, Nietzsche comes across as a quite self-satisfied mystic. And note the role that Dionysos plays in his later work. He even finally signs a letter as Dionysos. What I love about Ecce Homo is that it manifest that Nietzsche himself is one more prophet, crying in the wilderness. True, he is a sophisticated, critical prophet, but still, he has a message for humanity.
I suppose I often use the word religion as a metaphor for "the value system that structures a person's life." Does anyone live
without such a value system, except in transitional moments of despair?
A person can be systematically anti-systematic, but this is of course a contradiction. The transcendental buffoonery of an F. Schlegel (and the Dada movement?) can get away with this, by means of humor. The paradox can be embraced, as paradox. But this is where philosophy is tangent to mysticism and/or comedy.
Sartre wore the righteous revolutionary hat, did he not? Sympathizing with all the downtrodden victims of Capital, etc. And Heidegger's attraction to the Nazi party was connected to the same sort of righteous moralism. They come across as intellectual do-gooders. And this is not to slander do-gooding in general, but to point out how much moralism is implicit or explicit in existentialism. And quite obviously in Marxism as well.
I'm sure you mean something different by the terms nontheist and atheist, but on the surface they are quite similar. Of course no one term could ever sum up a person's views.
With respect,