I think this institution is trying to do two jobs and in these times it is not suited for it. Perhaps either or both aspects of it need to be renamed to help in separating them.
Our society affords certain benefits to people who marry. Those benefits are civil or legal. We should define precisely what is required of such a civil union. For example, could two friends form a civil and legal union? I think any citizen (or any two citizens) should be able to enter into this new arrangement, which I for the moment am calling a civil union. From that would accrue the benefits (more or less) of today: right of survivorship, legal next of kin status, right to “spousal” benefits from the partner’s employer, etc.
We should then separate and, preferably, rename religious sacraments around a couple bonding as a family. For the sake of this discussion, I will call that Pair Blessing. Various religions or whoever would be free to create their Pair Blessing sacraments and offer them to whoever their faith decreed.
All would-be couples would go through the process of civil union, which would be the primary event. Then, if they desired, they could also choose to have a Pair Blessing in their faith. The legal aspects of the current religious marriage ceremony would no longer be part of Pair Blessing. Pair Blessing would simply be a sacrament like, for example, confirmation or bar mitzah and have no legal status whatsoever.
I think these changes would go a long way to resolving the conflict and confusion and inequality of today.