“Government should have nothing to do with marriage.”
There has been no successful civilization that did not uphold marriage between and a man and a woman and the consequent family unit. That is the basis of civilization.
That’s not a rationale for government regulation. The UK had no such concept as civil marriage prior to 1836, and seemed to be doing ok for itself.
Is there any reason why we can’t return to a situation where marriage is a religious ceremony that happens in a church? (Not arguing for a return to the actual pre-1836 situation here which actually only allowed C of E, Quaker and Jewish marriages....)