Most of the debate when it comes to marriage today revolves around political issues (should this or that type of marriage be restricted by the state) or around Biblical justification (is this or that type of marriage allowed by Scripture). That, to my mind, is an immediate failure even if an understandable one.
In the last hundred years or so there’s been a dissection and distribution of a broken idea of marriage. That would take some time to unpack, but I’ll mention some strands to my thinking.
Take sex for example.