It seems to me that objective morality for you would be like God giving the ten commandments on stone tablets to his faithful servant Moses, a story you can no longer believe in.
But you can evaluate yourself as a hero because you don’t give up. You’re like Sisyphus. You persist following your dream here on ILP even though you believe it’s probably futile. No?
Martin Heidegger makes a nice case in point. In Being and Time, he writes 488 pages of original philosophy using obstruse language. That much material is bound to invite multiple interpretations. I have read that he thought Sartre misunderstood existential ontology. Did anyone get it right in Heidegger’s mind? I know he and his teacher Husserl disagreed on it.
I mean you can read Heidegger’s books for their ethical implications, but I don’t see him claiming an objective morality like you want. Human life doesn’t come with an instruction manual. Like Heidegger said we’re thrown into the world. With help from our culture whatever that is we achieve an understanding of how to act. Our ideals are images of the ultimate good or goods. Objective morality,if there is such a thing, lies behind the image.
If you want to see what Moses saw you’ve got to go up the mountain yourself. You’re not going to believe what Moses or anybody else tells you about it that you don’t experience firsthand. And even then you might doubt it when the shine wears off.