The real kicker is challenging the ideas that:I think we might be talking past each other or using the words differently.
Objective moral truth means that there is a moral agent who has established a set moral truth, meaning that certain actions are inherently good or bad.
The obvious agent, in this case, would be God but could be anything who has established such truth.
The approach you are describing is subjective morality, where we as humans establish what we believe is morally right or wrong. Which I think is what we have been doing since the beginning and also why our morality seems to be changing throughout history.
Subjective morality doesn't mean individual morality, that each person just makes up whatever they believe is right or wrong. But is arrived at based on a lot of things, one of them being our evolutionary history and culture.
Looking at a person like Hitler for instance, he didn't arrive at his morality all on his own, he was influenced by the time he lived, the culture he was raised in etc. All these allowed for his morality to dominate in the time he lived and convinced a lot of like-minded people that this was an acceptable thing to do.
The same way people in earlier history arrived at the moral "truth" that slavery was perfectly acceptable. If there was no moral foundation for slavery at the time, it wouldn't have occurred. The same way that we today for instance don't support beating children, even if some individuals do it, there is no moral foundation for such morality to get hold in today's societies. However, if everyone thought that beating children was a moral thing to do, it would be extremely common to do it. In fact, it wasn't that long ago that hitting children was considered perfectly fine, it wasn't uncommon for my parents for instance to get a slap here and there by the teacher if they didn't behave well.
Again if there is some objective moral truth, then hitting children would always be considered morally wrong. Yet there is no evidence for this being the case as I see it. History simply doesn't seem to support it.
-a creator makes inherent moral properties just by creation. If I use a straw to push paint on canvas, which was not what the straw was created for, that doesn't make it inherently evil or wrong, even if the creator said so.
-That someone outside that might-makes-right paradigm couldn't challenge the morality that agent outlines through other ostensibly objective criteria, such as utilitarian or consequentialist criteria.
-That agent doesn't also have a bias they are subject to, making their outlook also subjective.
-That an ostensibly objective agent's pov is accessible when *we* are all subject to biases and limitations. Making our beliefs and interpretations inherently subjective.
Imo even with a god or gods subjective morality is inescapable.