I suspect that philosophers know as little, in the absence of science, about ethics than they do about anything else. Rather, the reason philosophers make free, at present, with their ethical pronouncements is the same as the reason the Church made free with its astrodynamical pronouncements in the 17th century. The reason is that science has not yet investigated the subject with rigor.
Philosophy doesn't gather facts about reality within itself, whether we are speaking about physics or about ethics. It is as blind for one as it is for the other. Nobody is privileged to choose what is moral. Nature has its own standard for morality, and that standard is survival. What does not exist is worthless. And an improper moral system that causes its own destruction via that of its practitioners is worse than worthless; like a disease, it has a negative worth.
What philosophy does is concoct logically self-consistent narratives, which might or might not be the truth. Philosophy and science inform each other: philosophy informs science about correct procedure, and science tells philosophy what the discovered facts are and which of its narratives has been disqualified from being truth.
A philosopher who does not engage with science is blind to reality. He forever spins conjectures that he has no way of checking. He gets into arguments with similarly blind other philosophers who insist that their conjectures are superior to his, and none of them really know what the truth is because none of them has indulged in experimental verification. Their arguments are so much hot air.
You know the old saying among atheists: "As science advances, God retreats," meaning that once experiment has revealed the true nature of a part of existence, the older theological explanations quickly seem obsolete — if not outright ridiculous. After three or four hundred years of trying to refute a scientific explanation that is supported at every turn by every test, while at the same time having their increasingly contrived alternatives either disproved or shown to be rather suspiciously untestable, the theologians adopt the scientific explanation, grudgingly at first, but after a generation they are pretending that they had never thought differently.
Ethics is like that. Philosophers may claim to have knowledge about ethics because they believe it to be subject to their choices. Some philosophers may believe that they can create ethics by making their preferences known. On the contrary, I say. Those philosophers are wrong. Nature constrains the truth about ethics to the same degree that it constrains the truth about gravity. This truth is something to discover. It isn't something to be decided.
When you discover the truth about ethics, you might not like it. You might wish that it were something else. But it will be the truth, nevertheless. The approval of the philosophers isn't required.