"13.7 billion years ago the necessarily-existing perfectly self-sufficient entity decided of its own free will to spit out the universe, time, and causal reality."
To my mind there's something really off and silly about this but which I'm not sure how to phrase as a logical argument. It seems more natural to me that if there were a timeless source of time and causality, then time and causality themselves would seem to extend infinitely in both directions rather than having a specific starting point (or ending point). But, then, if time didn't have a clear starting point or ending point, you wouldn't need to invoke an entity outside of time to get it started. You could just say that it was always there. Or, alternatively, if it isn't silly to say that "13.7 billion years ago the necessarily-existing perfectly self-sufficient entity decided of its own free will to spit out the universe, time, and causal reality." then it seems like it shouldn't be that silly to say that the universe itself is all that exists, and it just happens to have a certain starting point relative to us because that's the way it is.
Really, my preferred model would be to say that time and causality do go infinitely far back, and, if this universe seems to have a beginning point, then that must mean that our idea of what the universe is is too small. Maybe this universe is a video game inside the real universe or something. And maybe the video game has a creator or maybe not, but in the wider universe outside this universe the creator might be fairly ordinary, and the wider universe could still not have a God at its foundation.