I agree with everything you presented there. That it is absurd to call the standard of “human well-being” a subjective point of reference for what is “good” and “bad” since those fundamental rules of the game of “human well-being” is all the innate attributes of just being human. Preferring life over death, peace over chaos, socialization over isolation, etc.
Not indiscriminately, but definitely not discussed and explained. They are dictations, not reasoned conclusions of mutual understanding. We can all improve on the 10 commandments in under three seconds. And we can all name off in our heads all the things that people can point to in religious texts that are barbaric to do, but biblical justified.
That is an example of why Secular Moral systems are superior to NonSecular Moral systems. The Secular Moral systems have an internal agreed upon goal of what to measure the good and the bad against. NonSecular Moral systems have an external imposed reference point that may or may not have it in the best interests of humanity for the good and the bad. No one can go grab your deity and force it to the table to explain itself.