We live at an advanced state in the destruction of Christian marriage by the secular (Left) state (aided by the mass media and all the other major institutions).
At first we had 'no-fault' divorce, which meant that marriage lacked even the status of a legal contract (so that just one party could dissolve the marriage, unilaterally, and without any sanctions). This continued with unlimited serial marriage, same sex marriage, marriage of 'trans'-sex persons, multiple marriage (half-implemented - accepted legally in the UK but not yet legally initiated)...
On the horizon we have non-human marriage (e.g. Men with animals) and marriage including children - these are mainstream-mooted, and 'logically' implied by consistent application of the current minimalist concept of marriage in terms of 'principles' and trends.
What we have (from a Christian perspective) is a social system where 'legal marriage' - the 'institution' of marriage - is (already, here-and-now) both corrupt and corrupting; and becoming ever more so.
'Legal-marriage' is already a manyfold-fake - we just have not adjusted to the fact.
Or, to put it bluntly, official-marriage is now evil: a creation of an evil-corrupt state; and 'arbitrarily' created, expanded, sustained or ended by that evil-corrupt state.
Add to this the 'convergence' of all the major, mainstream churches with the secular-Leftist state; which means that church-marriage is already just as bad as legal-marriage in most instances; and the real Christian churches that are current exceptions all display signs of being on the same path towards ever-fuller convergence as the mainstream churches.
In sum: a fake church cannot (and will not) sanctify Christian marriages.
So, the option of real-Christians having a separate system of 'church marriage' - to substitute for the legal marriage seems to be, at most, a temporary expedient.
And even if this expedient were attempted, it is clear that - while the Western state will tacitly (de facto) sustain the marriages of some religions (including allowing, and not interfering with, the operations of religious courts which may impose severe negative sanctions for marriage transgressions - including physical violence and even death); this will not apply to Christianity.
Quite the opposite. It is ever clearer (albeit only to those with eyes to see) that the unifying purpose behind the half-century of wide and expanding range of changes of law and practice in relation to marriage and the family, is precisely the destruction of Christian marriage.
The consequence for real Christian marriage, as I foresee it, is pretty extraordinary.
Christian marriage will need to become a personal commitment between a Christian man and woman. Full Stop.
Whether made in public or private, this marriage commitment will (ultimately) neither be validated nor sustained by any formal institution; neither state nor church.
Marriage will rely exclusively on the two parties - who cannot depend on help, or even encouragement, from anyone else... Who should, to the contrary, expect that institutions will continually be working towards the break-up of that marriage.
Meanwhile, 'official' marriage will go in quite the opposite direction; and more and more 'relationships' are recognised legally and socially; with the increasingly 'unorthodox' participants seeking the status, protections and sanction of an official marriage.
In the end, real marriage is the only (official) 'fake'; and only fake marriages are 'real'.
It may be that real Christians may be among the few people who do Not marry (legally).
We may soon be in an inverted-world where zero Christian men-and-women but instead nearly-everybody-else (in various combinations and numbers of men, women, other self-identified genders, animals, children, AI robots... who knows what?) will become the majority of 'married' (um...) entities.