Well, since it’s all made up, I guess you can claim whatever you want.

Two things about that (overanalyzing your shower thought):

1. Geneticists have what they call the "50/500 rule," which basically means that you need at least 50 people to avoid inbreeding, and at least 500 to avoid genetic drift. So while three people are 50% better than two, it's not going to come close to avoiding inbreeding.

2. If you read up on Lilith, including your Wikipedia link, you'll see her name only comes up once in the Bible, and it's not as Adam's wife. All the stuff about her comes from other things, including Babylonian and Mesopotamian writings, and lots of folklore from the middle ages. And at that, she's sometimes Adam's first wife, with different explanations about what happened to her that really in her not coming back to the garden, or she's a demon. So there's not much likelihood that she's contributing to the gene pool.

Because Lilith isn't mentioned in all versions of the Adam and Eve story, and certainly isn't mentioned in Genesis. There's plenty of versions of the story with lots of different characters, and plenty of interpretations of what happens, but in the Canonical Christian Bible, there are at least two events where the entire human race is only directly described as being one single family - Adam and Eve, and Noah's flood.

Because Lilith is not actually mentioned in the Christian bible despite this wiki page's attestation she is mentioned in Isaiah. She only appears in rabbitic literature.

Lilith is also the catalyst to a lot of vampire myths often described as the mother of all vampires.

Lilith left Adam after she refused to become subservient to him and then would not return to the Garden of Eden

Based.

All Hail Lilith, The sacred mother of Feminism

Which might be relevant if those were real people. You might as well worry about the genetic makeup of Pokemon

Incest doesn't inherently cause genetic disorders, it just increases your chance of being born with recessive genetic disorders. Most of those disorders are mutations, and if the Garden of Eden is so perfect there probably aren't genetic disorders to start out with, meaning incest is fine from a genetic perspective. All the genetic disorders would be mutations later down the line. Maybe they're punishment for the original sin or something, to fit it into the themes of the story.

Sounds like a shitty retcon from an series that jumped the shark

I don't think creationism is particularly bothered by genetics.

Anyone feel like this is just the story of some douche who divorced his awesome wife to find a subservient slave wife and over thousands of years its become part of a religion?

“Oh that Lilith we don't talk about her she was a demon” he tells his grandson and 200 years after the story people interpret her as a literal demon, and just gets wackier and wackier as time goes on. Kinda feel like you could explain all that Abrahamic lore that way.

Can't have an ancient story without an evil woman you can blame everything on.

Fucking your half-sibling is still incest.

Couldn't God just create more humans after the first three? Is it certain that he creates 3 and then explicitly stops?

Lilith mated with demons not humans.

Also Adam lived quite a long life. Like several human lifetimes

Then there is this fun titbit.

Adam withdrew from Eve for 130 years after their expulsion from Eden, and in this time both he and Eve had sex with demons, until at length they reunited and Eve gave birth to Seth

If you're grasping at cousins as being the sole separator you know you have a problem. But also there's a lot of conflicting information, such as Cain settling in the city of Nod east of Eden which suggests I guess that there were people outside of Eden already. Don't take anything too literally, and jokes are jokes.

Thing is, Lilith didn't pop up in texts apart from post-Jesus, such as talmudic texts. (although a Lilith was mentioned in Isaiah, it could have been a demon of some sort) so she'd only really be regarded by modern day Judaism, not by Christians.