"Socialism is good because it's a more equitable distribution of resources, which leads to greater happiness and a society with less poverty because xyz."
"Veganism is good because it reduces the harm done to animals and the harm done to humans working in the meat industry, who have far increased rates of PTSD compared to the general population."
These arguments will only convince you if (i) you think an equitable distribution of resources is better (ii) less poverty is better (iii) xyz is a convincing reason to think there would be less poverty (iv) harm to animals should be reduced (v) harm to humans should be reduced (vi) incidence of PTSD should be reduced.
These philosophers do not say there is some law of the universe which mandates that less poverty is better, or that PTSD is bad. The reasons why you should think those things, they would say, are second-order reasons. There may be some other paper arguing why PTSD in society is a net negative. That paper would ultimately read something like "icreased PTSD rates lead to increased rate of suicide/lower economic efficiency/harm to other humans". There is no single argument why harming other humans is wrong, only axioms that we would take as our priors, just as we take it that "A != !A". They just seem right, and you don't have to subscribe to them yourself.
Unlike religion, all philosophers can say is "it would be advantageous to generally valued goals X,Y,Z that we take these axioms for granted". It turns out that enough people share these axioms for this philosophical work to be useful for navigating difficult questions even given those axioms. Again, you don't have to share the axioms, but if you do, a logical argument can be produced from them, one which it would be to your embarrassment to ignore without any refutation, still assuming that you hold the axioms yourself. Again, you need not do so.
Similarly, the advice from a physicist about the heat tolerance of the hull of your rocket ship would need to balance both economic and other interests. If you don't care about going into debt, you can sey hell to the economic arguments, and use the best materials possible. If you don't even care about your ship launching, you can say hell to the physical arguments about tensile strength.
What I'm trying to convince you of is that philosophy is about as useful as any other field of inquiry in the sense that it attempts to argue from axioms most people hold already (therefore it is not a niche field) and it produces conclusions that such people can use in making choices day to day (therefore it is not a useless field). I think that no matter what particular axioms you hold, there is some philosophy which argues from those axioms out there somewhere. You yourself make philosophy. I'm not producing an argument from authority here.
Can you cite a philosopher arguing that the universe itself mandates that veganism is correct?