To redeem this situation, the (conservative) churches must agree to restore marriage as a sacrament reserved for their churches and their rules. This requires several things:
1) They will only recognize marriages done by their churches. If they are married outside of the church, or another church with similar rules, that marriage will not be recognized by the church.
2) Those currently married outside the churches will need to be at least administratively remarried by the churches.
3) Secular recognition of their marriage is optional. That is, if married by their church they are married, whether they have a government marriage certificate or not.
4) Likewise divorce is determined by their church, and they must agree to ecumenical divorce if one or both leave the church. Optionally, terms of divorce might be prenuptially determined by the church before marriage.
Lots and lots of other rules, but the idea is to take back the sacrament of marriage from the state.
When you say “the church” what do you mean?
The church is people not a building.