If you fail to see the connection between the two then there is little to discuss. When an increasing number of post-Christian Americans are cohabitating instead of marrying, then certainly the divorce outcomes have to be examined as one of several reasons. As far as your post above, churches should completely separate their concept of marriage from that of Caesar; Caesar’s contracts & conditions are what keeps many away from it.
The church's concept of marriage can do little to protect children financially at divorce. Civil law will always be necessary. It should protect minors; in practice, it enriches many in the divorce industry, such as attorneys, mediators, forensic accountants, child therapists who may be drawn upon to give testimony, et cetera.