the pre-Abrahamic accounts of Genesis would be written aprox 1000-2500 years after they took place and major accounts like the creation, flood and separation of languages would have many competing accounts from surrounding cultures, especially those who are more advanced.
Whereas the Abrahamic accounts themselves would be a lot closer to the time they were written and have no competing accounts because Abraham's story is uniquely for the Hebrew's and no one else so their high value of preserving their detail is far more likely. Also, the Abrahamic accounts are far more detailed than the pre-Abrahamic accounts which also suggests more accurate information.
What we have is post-exodus Hebrews with very little detail about God and a propensity to surrender to pagan ways as evident in many accounts. They were quick to complaining and lacked trust in their direction as a people and their leader, also evident in many accounts. This points to pre-Moses Hebrews were probably unorganized in leadership, had a poor understanding of God, had no to very little systems of official faith and probably were saturated in pagan ways or some sort of hybrid folk faith. and what do you expect with no guidance and left to their ways for hundreds of years?
Moses had a task to unite the people, start a monotheistic system of faith and orthodox beliefs, and cleanse pagan elements from the Hebrews, an entire generation had to die off to prepare the Hebrews to go the promise land so this points to very deep seated values systems that were counter-God.
This in no way disvalues literal accounts from the rest of the Bible. it just looks at the early Genesis accounts far removed from the time they were written with a greater focus than surface literal details, such as to de-paganize the post-exodus Hebrews and points to the one true God, creator and sustainer of all things.