How would we be absolved if we know that we are "sinning". I put that in quotes because it's hard for me to believe that by "sinning" or doing something wrong, I'll be judged after I die. Wouldn't that just leave us more accountable for the things we do?
We're absolved from sinning because, as you said, it is what we define it as. That makes it highly subjective, certainly not fit to be applicable to a mass of people, unless you have intent to control them. Sin could be viable in a personal context, much as Sandy has just said, but the dogmatic dichotomy in religions of "this is wrong" and "this is not" is fit only for mindless sheep. In that sense, we are absolved from that kind of widely used connotation of the word "sin".