These discussions get vibrant, heated, or comical. I personally read these only for the humor, because the rest of it is completely useless.
In reality, there are many possible causes for the breakups of engagements and marriages. The value of discussing these is to know what not to do. But these forums are never diagnostic for any specific case. And it is often that well meaning people claim to know a lot about a couple while they truly know almost nothing.
I can easily list a few dozen variables that have not appeared in any comments before this. Unless we divert the focus to identifying the “what not to do”, the time spent in typing will have been a total waste.
Marriage expectations have evolved as the culture has changed. The support for the battles to dissolve marriages has also grown rapidly. The toughness that people have in approaching their own marriage crises in which there are demands for change and resistance to them has also escalated. Yes, there are mismatches. We also have myths about “learning boys” that are hard to change. We enter marriage poorly prepared, and sometimes with very distorted views of what it should be. Parents interfere. Forums of social interaction contribute handsomely to support ending marriages. Divorce is less stigmatized. And the list goes on and on. This is just a small sample.