I think you'd first need to elaborate on what you would perceive as "divine inspiration" before you can make that claim.
I take an Existentialism viewpoint, and at any turn of history, the morality that we have IS a human consensus. There is no other way around it in terms of how we perceive it to be. But mere consensus is NOT ENOUGH to serve as a moral grounds for anything, because we are talking about moral pluralism, in which case there is no common ground for including minority opinion.
On top of that, in your case, you seem to ignore the continuum of development as to how you got where you are in the first place. You seem to be critiquing these issues from some vacuous elevated position of "present day morality" as though you've arrived there apart from any foundational development that took place over several millennia that you merely inherit.
If you can demonstrate that we got here apart from the Judeo-Greko-Roman-Christian moral foundation we have... you'd have a point.
Biblical laws, especially in OT ARE defined as contextual nuanced principles that define a legal system of a nation in context of whatever environment such nation existed.
The environment of the day was harsh, and you simply can't apply our modern-day "abundance-driven morality" to their day where such abundance was lacking. There would be different moral context if you had unlimited supply of water, as opposed to you have only enough water to sustain X number of people.
It's a much more nuanced reality, where moral dilemmas are not some hypothetical concept, but something that people would face daily. In such, what's "jacked up" is the environment that these people are against and have to claw and band together to survive. In such, the context of morality is quite different.
Of course.

There's no question about it, but if America would be reduced to apocalyptic wasteland due to some event... then all of the "American morality" would be largely irrelevant to the context in which it existed in. It would be much more nuanced and unpredictable reality filled with moral dilemmas that constantly conflict moral ideals.
My grandmother survived Stalinist Holodomor, and she was telling horror stories about people who fed their dead children to their surviving children. Thus, you have little clue of what some people have to go through when it comes to picking one moral ideal over other.
I would not say that morals are "subjective" as much that morals are contextual. These describe ideal paradigm of behavior based on context that such behavior exist in.
For example, a person would be considered a nutcase if they would all of a sudden began acting like a rock-star in the middle of ... let's say a funeral. If they are on a stage at a concert, then the context is more fitting.
Thus morality can be absolute in certain contextual setting of that absolute.
Likewise, morality and knowledge are not separate concepts. Morality is a subset of what we would consider knowledge, and it exists as a network of interrelated behavioral concepts. What we would describe as "morality", would be a subset of contextual concepts and principles that we consider to be of utmost importance for our survival.
Hence, you are confusing objectively best possible scenario given ALL KNOWN possibilities, and "best possible" contextual behavior in a scope of SOME known possibilities.
Likewise, there's some pragmatic concepts to consider like, what is morality for? The obvious answer would be to serve and direct our behavior in such a way that ensures our survival and flourishing.
Back to the example of my grandmother. Would it be immoral to feed your dead children to your other children? Well... nominally it would trigger an SJW Earthquake if that would happened in American culture today. But if you move context of a desperate mother trying to get her children through a winter where all of her food was taken away... it's a different context. It's a context horrors of which few people can possibly imagine.
Hence, there are nuances to consider that are not immediately obvious.