Certain ways of doing things have a natural logic. Doing them differently can be at least pointless, or even damaging. For a simple example: human beings are designed to walk on two legs, not four limbs or on their arms. To do so, unless you have a disability and can't use your legs, is pointless for a start and can be damaging to the body because the load-bearing is on limbs not intended for it.
This applies also to sexuality. There is a natural and right way for it to happen, and variations on it may not just be individual preferences. They defy natural logic or law.
Sexual relations have two intended purposes if approached in the right way: the affectionate bonding of the two participants and the conception of children. Even if someone is not convinced by Christian teaching, or Jewish, or any other, pure logic shows this: the only kind of sexual relations that meet these two purposes is, consenting sex between adults of opposite genders. Any other form fails to meet one or both of those criteria.
Sex between two people of the same gender cannot produce children. It is naturally illogical.
Sex between a human and an animal cannot produce children. Apart from the disgust it may cause, it is naturally illogical.
Sex between an adult and a child can be traumatic or injurious to the child. It does not cause affectionate and safe bonding between the people involved, so it does not serve both the two purposes intended.
Forced sex, or rape, is traumatic to the unwilling partner, and denies to notion of affectionate bonding. For that reason, as well as denying the victim's rights, it is a bad idea. It can hurt someone, so it should not happen.
Sex involving multiple partners can cause uncertainty about who the father of a given child is. It also denies the bond between two individuals, dissipating it among a group.
Sex among strangers, with no real connection, denies the idea of bonding between the people involved. It is physical intimacy without emotional intimacy, thus a clash with the ideal of affectionate bonding.
God made things a certain way. Trying to vary it leads to dysfuntion and adverse side effects. God makes rules for our sake, not to be a spoiler.
Stick to the plan.