Earlier quoted context omitted.
How exactly is "marriage" failing? This notion that two people being in a long term relationship can somehow suffer systemic failure or attack is bizzare. No objection re: children though. We've done an absolute number there via cost of living.
How is it bizarre? It seems the same category as saying friendship is failing, which also is a reasonable claim; see the entire bowling alone thesis. I'd probably group them all under the umbrella of social connections failing, which I'd consider one of the biggest issues of US society today.
Which is to say their doesn't seem to be any indication that "marriage is failing" i.e. there are less people in marriages. It's also notable that the rate of cohabitation has tripled over the last 20 years[2] (included because it's a worthwhile proxy for things which are long term relationships but might not be recognized as marriages).
Where I can point to fertility rates across the Western world falling to below replacement and say "yeah we've got a problem", the notable thing is that it seems thoroughly uncorrelated with people being in long term relationships. People might not have time for friends, but there are more committed relationships around then at any time in history - by the numbers.
[1] https://www.statista.com/statistics/183663/number-of-married...
[2] https://www.census.gov/library/stories/2019/09/unmarried-par...