The lottery could really represent any tradition or practice that now seems outdated, meaningless, or even inhumane. The story conveys just how important it is to keep evaluating traditions for their value and not simply to continue them because they are traditions.
Once upon a time, slavery was a tradition. Obviously, that tradition was reevaluated and considered to be inhumane, and so it was done away with. There was a time when women's subservience to men was a tradition; women had to fight, tooth and nail, for the right to vote. That tradition, of the legal submission of women to men, was reevaluated and cast aside. (Of course, racism and sexism still both exist.) Racial segregation was a tradition for many years, but "separate but equal" was found to be an impossibility, and so the country underwent the process of desegregation. Not so very long ago, same-sex marriage was banned, as marriage was traditionally something possible only for a man and a woman. However, that tradition was questioned and the Supreme Court decided that it was discriminatory, and now we have marriage equality.
In a broad, general sense, the lottery system from the story represents old traditions that people blindly follow for the sake of following tradition. The people in the story do the lottery and the death by stoning because that's what they have always done. They don't question the morality of it or even the purpose of it. They just do it even though nobody remembers exactly why. Old Man Warner gives the story's only clue as to the original purpose of the lottery.
"Used to be a saying about 'Lottery in June, corn be heavy soon.'"
It seems like the original purpose of the lottery was a sacrifice to secure rain for the crops. Readers are told by Mr. Adams that several other towns are giving up the lottery, which means that the lottery doesn't make sense or doesn't apply to those other areas. It seems that Mr. Adams supports that idea, but Old Man Warner replies, "Pack of crazy fools." That indicates that Old Man Warner supports the lottery tradition no matter what.
If the question is asking for a modern example of a tradition that just doesn't make sense anymore, then I would look to weddings. They are full of weird traditions that just don't apply anymore. For example, the father giving away the bride seems quaint, but the reasoning behind it just doesn't apply anymore. A father would give away his daughter because she was his property to give. He would give his daughter to the husband in exchange for a dowry. The idea that a woman is a piece of property to be bought and sold is not only archaic, but demeaning.