Marriage has become almost meaningless'at law. That doesn't mean we should ban it. It does mean something to most individuals and their religions.
Until recent decades marriage was a religous sacrament. Governed and performed by churches. In earlier times a man and woman would go to a tent together and emerge married. In many religions divorce is also a matter for the couple.
Some confusion has arisen because temporarily the state has become involved in recording marriages. It had to do this because marriages had legal meaning. Marriages now have no legal meaning yet the state involvement remains as a legacy.
Marriages used to be "to love one another only", adultary was a crime. They used to be "to death do us part", not anymore. Children had to be born in wedlock to inherit, not any more. Custody of children required marriage, not any more. Defactos have the same rights as married couples.
The rationale for the state getting involved in the religous sacrament of marriage has gone. Marriage is a matter of individual conscience and religion. The state has no place in it.
The state should get out of the marriage business.