No, it doesn’t depend upon metaphysics. It depends upon the society, the accepted cultural values and views, which will define the ethics and, thus, the morality of the decisions made. This is what Philosophy does - critical thinking.
Take cloning, for example. What does the USA thinks about human life? What value does the american society give to a zygote? And an embryo? Based on those values of that specific society, what would be ethical and what wouldn’t be ethical for us to do in regards to cloning? Can we clone a human ear in a rat’s backside? Can we clone a human liver in a petri dish? How much can we meddle with human beings without stepping over individual human rights?
And Philosophy gives answers: this society considers human being to be X. So we can’t clone X, or we’d be stomping over human rights, since we’d be subjecting a human being to experimentation that could pose a risk for its health. We can clone a human ear in a rat’s backside, since a human ear is not a human being. We can also clone a human liver, by the same logic.
So on, so on.
And metaphysics? That comes when one tries to define values, as this is a more abstract concept. But Philosophy, you’ll find out, works with MORE areas than only metaphysics. There are philosophers trying to explain values and morals using Evolution (caring about each other was naturally selected, for example).
Or did you think that ALL philosophers believe in God/sobrenatural? Some try to give meaning to concepts such as “values” without relying on a spiritual force compelling us to do good. Some offer evolutionary explanations, cognitive developments, sociological influences, proposing a possible answer to the foundation of “morals”.
For you, it may not be enough. “Ohh, but there is no consensus!”. Which is why I say: then, thank goodness we have Philosophy. Perhaps one they they will find an answer, like they did for so many other problems!
Philosophy is too large a subject, which is why so many other subjects got separated from it: like maths, psychology got so complex by itself, that it became a science of its own. “Science” as we know it was once called “philosophy of nature”.
You can dislike Philosophy as much as you want, but it hardly is useless as you put.