Arguing that legal marriage should exist simply because it existed prior to the formation of the union is silly. Many things existed prior to the formation of the Union.
Look, anywhere you give government power is bad and that extends into even the more traditional social concepts. The execution of marriage as it exists today in greater society is ridiculous on its face. And that is primarily a result of the interference of government and it’s rules. Rules that are defined and manipulated by politicians.
Your thinking is ridiculous, goofy, in your efforts to destroy marriage, now you want to pretend that your thought out position is that the people of America will just eliminate marriage, and marriage law and divorce law.
According to your fantasy, we would always have had polygamy and gay marriage, and somehow marriage, families, and divorces would be invisible to society and law.
Stop the silliness.