Humans already have rules, both legal and social, that detail our obligations to one another and society. But since these rules can be derived from first principles, they don’t require any god or any religion, and therefore provide no extra-societal power or control.
Enter “sin.” The most unforgivable of which is not believing or submitting to this nonsense in the first place. If you don’t recognize their self-declared authority, then they can’t control you, and that’s just unacceptable. Which is why non-believers are to be shunned or killed, lest they undermine the scam.
You’ve probably encountered someone who says something like “we all sin, we all do bad things.” Every time I’ve heard that has been them attempting to justifying their god and its rules, but particularly while rationalizing the fact their superstition says that their god tortures people for eternity. As if this is all that needs to be said about eternal torture.
"Sin” and “bad things” - that is, morally wrong - are two completely separate categories that they’re trying to make synonymous. Selling you the Bailey disguised as a Motte.
In the lists above, ignore the rules that are already codified in law and existing social obligation, that you’ll find all around the world because humans have successfully figured out what’s important to facilitate co-existence. Like murder and theft. When you’re killing and stealing from each other, social cohesion evaporates, and the tribe quickly dies out. So, duh. These are rules that are merely retelling and not revelation, that humans have understood for thousands of years. These rules provide no new information and are only there for the illusion of moral authority, an air of legitimacy, even as the religions themselves outright prescribe killing. Their inclusion lets them pretend “sin” is the same as “bad” and that religion is the basis for morality in the first place.
The remainder, originating solely by religious doctrine, are completely self-serving. When they’re not demanding the promotion of religious dogma to others, they’re either control-freak rules about pointless minutae (e.g. foods, which hand to wipe with) based on superstitions as juvenile as “step on a crack,” or they’re destroying self-esteem by making it a “sin” to not hate yourself, to be ashamed for how your body (that “god” designed) works - e.g. masturbation, sexual attraction. Or declaring certain emotions or reactions un-glorifying to “god” and therefore worthy of shame.
It’s probably quite common to be interrupted while masturbating, or to be a little regretful for reacting emotionally in the heat of the moment, and to wish you’d kept a level head. It might be embarrassing, you might have regret, but it doesn’t make you a bad person. Yet these are amplified as “sins” to foster shame over non-issues and offer you the solution to that shame.
That is, they de-humanize humans, reviling humans for being human. Demanding people to be “perfect” in a way that is arbitrary and doesn’t even make sense. Especially if the “god” is responsible for our existence and nature in the first place.
And then the real scam, condemning them when they, inevitably, are not perfect, and offering the “fix”. That is, they create the imaginary problem, and then offer the imaginary solution.
“Sin” is new, invented ways for you to feel like you’re not good enough, for the religions to agree and really drive it home that you simply aren’t, and then, conveniently, offer the solution to the problem they created or fostered in the first place.
