"Marriage has always had to be legal, or it didn’t count outside of the people who were rooming with each other."
Why - particularly in this day and age - does marriage need to be "legal"? The state does not say that only married people can live together, or have sex, or have children, so why should there even BE a LEGAL entity called marriage? All of the moral and social reasons for it have been disputed by - and mainly abolished - by liberals. Why shouldn't churches just perform marriages as a sacrament or religious vow, without registering with the state?
You can do what you want, you could do that 50 years ago, and 250 years ago, and 2500 years ago.
If you don’t care if the law recognizes your marriage, then don’t comply with the law.
Thomas Jefferson and George Washington wanted legal marriages, but that was their choice, others didn’t, and don’t need to, if they don’t want to.