Moral relativism, is-ought, and the placebo effect

Hello Rabbi,
Full disclosure – a secular guy who reads your book “God Plays Dice.”
It is argued against atheistic views (as you argued in your story) that it is impossible to formulate a moral code from facts. Also, that without God we fall into moral relativism and that what is “bad” or “evil” is merely my opinion. Therefore, God gives objective validity to one or another moral theory.
My questions are like this:
Don’t believers themselves fall into subjective relativism, because their god is one of many that they believe in – meaning that there are other gods in the universal human pantheon, each of whom claims the truth?
And if so, could it be that God actually functions in our lives as a psychological-social placebo effect? ​​That is, belief in God helps us make things “true” even though it is logically difficult to define many social and moral axioms as “true.” All this without any “physical existential realism” implication per se. That is, that “there is no” God, but belief in God is essential to us.
Thank you very much for your time.