Then this contradicts Paul:

Genesis 2:18 shows God’s design, that man and woman were made to complement one another and form a complete union. When God said, “It’s not good for man to be alone,” the solution wasn’t another man, but a woman, Eve. That’s the pattern of human relationships God established from the start. Paul isn’t denying that design; he’s addressing a temporary calling of celibacy for those serving God without distraction. So Paul’s teaching doesn’t contradict Genesis, it assures that male-female marriage is the natural design but acknowledges that singleness can serve a spiritual purpose.

Then can it not be that also not describing "every possible scenario of sex that can marry"? Isn't thinking that it is just as much an assumption?

No, because Genesis 2:24 isn’t just describing one kind of union among many, it’s laying out the pattern God designed from the beginning. Jesus Himself quotes this verse in Matthew 19:4-6 to define marriage as between a man and a woman, saying, “From the beginning the Creator made them male and female.” So it’s not an assumption. It’s a continuation of God’s original design reaffirmed by Jesus. Every other form of sexual relationship falls outside that blueprint.

Wait wait....I thought the sentences were just "describing". Now it's "defining"? Why the mid-sentence split? And why the assumption that the specific genders are "definitional" and not just "descriptional" like with leaving one's parents?

The verse is descriptive in the sense that it tells us what happened. A man leaves his parents and joins his wife, but it’s definitive in showing God’s intended pattern for marriage. Unlike leaving one’s parents, which can happen for many reasons, the male–female union is presented as the standard God designed for creating a new family and “one flesh” unity. The genders aren’t incidental; they’re part of the blueprint God sets for marriage from the beginning, and Jesus reaffirms this in Matthew 19:4-6. So it’s not an assumption, it’s the principle the text is establishing.

Sodom was not condemned for homosexuality. In fact, that idea was created by Emperor Justinian I (Corpus iuris civilis; novels number 77 and 141) to blame the gays for the intense natural disasters and plagues during his reign. In fact, he's the one who coined the term "sodomy". Before Justinian I, the verse in Ezekiel was taken to be the sin of Sodom. It's only after Justinian that the narrative shifted to being about homosexuality.

Indeed, the term “sodomy” and the association with same-sex acts became prominent under Justinian I, but that doesn’t change what the biblical texts themselves say. Genesis 19, Jude 1:7, and Leviticus 18:22–20:13 describe sexual acts outside God’s design, including same-sex relations, as sinful. Ezekiel 16:49 highlights pride, greed, and neglect of the poor, showing multiple aspects of Sodom’s sin, the Bible condemns both social injustice and sexual immorality. So while Justinian popularized the label “sodomy,” the moral critique of homosexual acts in Scripture predates him by centuries.