You are conflating two concepts, sin as religious concept and sin as “morally transgressive” concept. Because much of what you describe regarding guilt, OCD, depression arise from morally transgressive acts (eg regret for treating loved ones poorly) that nobody denies the existence of; what people increasingly deny is the spiritual concept of sin, which depending on the religion often includes things that aren’t unambiguously morally transgressive (all cultures consider stealing and unprovoked murder wrong, but breaking kosher is only a sin in Judaism because it’s a rule they think their god commanded of them).

I do think it’s true that many cultures have some kind of ritual by which you can absolve yourself of sin (be it religious or areligious), though not necessarily sacrifice. For example in Christianity the act of confession files the role. In the secular world this role is mostly filled via therapy, but a lot of other people choose to fill it with things like volunteering (someone who did a lot of bad things during their addiction may get involved in addiction outreach or speaking). I suppose given the time or financial cost of these activities they do represent a sacrifice in some way though.

Anyway, I agree that everybody has some concept of “moral transgression” which you as a religious person might call sin. But I don’t think it’s denied in contemporary culture at all - to the contrary, with things like cancel culture and such, we are much less willing to allow many sins to go unpunished - nor do I think “sacrifice” is necessary to mentally recover from the guilt it induces.