I think Vonnegut is just putting forth the notion in his own playful way that meaning and purpose is not delivered from on high by non-existent supernatural beings anyway.

It mirrors Alan Watts a bit when Watts said he considers the Gospels "inspired" (or other "sacred" texts), but not in the sense of taking dictation from the almighty, but rather human beings attempting to craft something they felt allowed them to make sense of the world around them.

So many of these texts are just a retelling of previous myths culturally updated to an extent. There's tidbits of wisdom here and there, but there's problems in the in insistence on literalism as well as the claims of a divine source.

It's a bit ironic that the so-called sacred texts are of part of the process of human beings trying to figure it out for themselves, even when done in a way wholly counterproductive.

Remarkably enough, sometimes their flights of fancy touch on the truth. If I recall correctly, the Hindu view of the process of creation and existence somewhat matches what cosmologists have theorized in their concept of the oscillating universe.