Marriage has declined because of No Fault Divorce.
Used to be: if you were dad, and you decided to run off with Sally, 20 years mom's junior, you did so at pain of losing home, custody and being sentenced to life-time alimoney. At least Sally knew you loved her!
Used to be: if you were mom, you lost interest, got bored, read Eat Pray Love and didn't feel your marriage was meeting your needs, or maybe had a daliance ... you could leave, it's a free country ... but not with the kids.
It basically comes down to something this simple: if you are not ready to take on no-fault divorce, you are not serious about fighting the decline of marriage.
So yes - it is individual responsibility, but you know what?
The government enforces individual responsibility through courts - sign a contract - and it will be enforced.
Even libertarians need that and understand that. Should we be moral and virtuous and eschew vice?
Of course. But there is a political philosophy that relies entirely on the upstanding moral decisions of individuals for a society and economy to cohere - it's called anarchy.
With marriage - where rules and the personal biases of agents of the courts still reign, but where contract has been thrown to the fire, what remains is a cesspool. Is it worth fighting for? Well - as a central organizing institution of civilization - probably. Are conservatives helping? Examples are sparse.
Taken from a comment in reply to Lowry's essay about the recent decline in divorce and increase in cohabitation.