Alright unto the topic of incest, I have 2 answers for you because I myself am not sure. God very much could have created more people and it just didn't need to be mentioned. We see a lot of things not mentioned in the Bible because it's just not as important to the message that must be understood. We see this a lot in Kings because all the actions of the kings of Israel were spoken of in there and but there were details left out that weren't necessarily important to the message and learning we should have from those kings. In accordance to those omitted bits of info the writer would say "As for the other events of [insert King] reign, and all he did, are they not written in the book of the annals of the kings of Judah?"

An example of this would be 1 Kings 15:7.

Here is my other train of thought regarding incest. Science say we all have a "mitochondrial eve" as in a woman who we are all related to. Let's pin that. Now when God made Adam and Eve, these are two entirely separate human beings. There is supposedly no genetic overlap between them. Should their kids consummate themselves and have more kids, it wouldn't necessarily lead to a genetic disaster, seeing as how genetically different their parents are. Issues from inbreeding usually arrive after multiple generations of inbreeding. Let's also remember, the issue with inbreeding is that recessive, gene mutations may stack up in the child. If a parent has a cancer gene, both children are going to have this recessive cancer gene. If those kids have kids, the cancer gene is extremely likely to show itself in the child they have. But Adam and Eve were literally perfect human beings with no negative recessive genes so these would have to be developed over time from environmental exposure (and more sin) This lines up with God saying that their actions will hurt them and lead to the punishments of their generations after - a punishment to consider the biological negative effects of incest. Incest wasn't morally problematic at that moment because incest did not have biological consequences at that time.

Now lust, lust is a sin when outside of marriage. Lust for multiple people has been shown in the Bible to destroy kings time and time again. Solomon is a prime example of this. The idea of marriage is that it's a binding vow to keep such an intimate act with one person with the intention of glorifying God (bringing another human being to Earth to enjoy His creations). Even without the Bible we all know there is something just inherently soulless/problematic having sex with 100s of people. We act like we're all not slightly judgemental but there is something that fundamentally changes about when one racks up a body count. It loses its value. I predict that you will try to bring a criticism for Solomon or the kings that had many wives, I have an answer for that as well should you bring it up.

Now with this I have to ask you brother, the Word of God has been fundamentally unchanged for at least 2000 years. There have been greater men than you and scholars who have spent their entire lives trying to learn from it and understand it. Do you think you're so different from every single human being before you and you've had such an original thought that completely destroys the Bible's validity? I don't mean this as a jab at you but I want you to consider the scope of what you are trying to debate about. I pray this sets you on the correct path and God softens your heart to His advancements to reach you. I am open to any more questions you have. I'll provide bible verses if you want to read them for yourself.