Either morality is still in development, or it isn't.
If it isn't, then presumably the best morality is frozen in the Bronze Age, when the great religions of the world were being developed. Thus, if we don't keep slaves, stone unruly daughters, treat disease as the product of unclean spirits, and encourage widows to throw themselves on the funeral pyres of their husbands, we're being morally lax.
On the other hand, if morality is still developing then it can only do so from a better understanding of humanity and the world. That understanding comes from science, history, discussion and compassionate reflection. We know a lot more about our world and each other than did the ancient founders of Bronze Age faiths, which means they cannot be treated as absolute moral authorities.
And once their absolute moral authority is called into question, then every moral injunction must be tested -- not just once, but constantly -- against what we now know.
In other words, we must think for ourselves.
There are multiple examples that illustrate immorality based on modern standards. Muhammad married a 9 year old for example. Either you have to take their morality in reflection of their time or you have to ignore certain morality. If you do either then it makes the morality imperfect which contradicts the way these books are sold as "morality guides".
Their message was that humanity is in dire need of salvation from sin. The moral perfection of the Bible was Jesus Christ. And he remains so to this day. Even now, humans are yet to find moral perfection. Our immoral nature still dominates our thinking and actions.
Whatever fallen behaviors recorded in the Bible are no more immoral than the fallen behaviors of today, verifying that we are all sinners.