Science develops models of the mechanics of the universe. Some are very simple and fundamental (such as the law of falling bodies) and some are complex and abstract (such as the tendency of mammals, including humans to stay loyal in the prisoner's dilemma, paradoxically when they're better served in the immediate situation to betray). Yes, some scientists who focus on the harder, less abstract sciences may not like the more abstract ones with fewer absolutes, but they are sciences and still provide us with predictable results.

You're right that no-one is an authority on mores, through religious ministries do try to assert that they are an authority (or are able to find scripture that attests that their opinion is right). But there is a scientific approach. Firstly, there's the matter of what social mores have evolved (and some, such as the ethic of reciprocity, have) then (defining morality as an aspect of systems of social organization) what known human history shows about how our social systems fail, and the mores that facilitate the longevity of those systems (or quicken their dissolution). So while science can't tell you what you want, the models we have can inform how we might get there.

Moral philosophy covers not just what should be right or wrong, but how to derive action from it and how we fail to do so. The whole Trolley Problem thought experiment, while it is an example of a paradox of deontological ethics (by taking a wrongful action you can make a situation less terrible), the variations show us our emotional assessment of the scenario strongly informs what action we see as suitable. It's easier to pull a lever to switch the path of a trolley. It's a lot harder to personally execute by handgun an innocent refugee to save their fellows. Hence why there's so much controversy on Kant's take on deontological ethics. (Kant wouldn't lie to Nazi Jew-hunters to protect the lives of Jewish refugees, though he lived before the Holocaust, so the scenario was the Murderer at the door.)

So my take from moral philosophy is one backed by countless scientific studies in the late 20th and early 21st centuries: We naked apes don't adhere to mores but feelings anyway. For day-to-day living this serves us well, but as the fascists take over in the United States, it's evident that has its limits, and is even putting the species at existential risk. The question is not if we can find a better morality, because we don't care what Jesus said (or anyone else), rather if we can find psychological tricks to nudge the population towards a more ethical system of organization. And that will take more science.