It has nothing to do with time spent and everything to do with having first hand experience of some of the issues that are not generally present in solid marriages.
I read your post to my husband the other night.. .he said exactly what you said here...of course this makes sense.. many of us haven't
walked in the shoes of being cheated on , or finding oneself in a "caretaker" marriage, dealing with someone depressed, mentally ill, sexless, etc..
We really don't KNOW how it would affect us and it's so EASY to say .. just Leave.. just "MAN UP".. just this.. just THAT...
I surely have more compassion on a giving spouse over one who is too busy, rejects too much, is harsh, plays silent treatment games..
But all of us have seen the fallout of others in our lives, haven't we...or still have enough empathy (hopefully) imaging being in THAT situation.. It's similar to feeling a Priest should never counsel a married couple or a woman, maybe a NUN, a single Aunt who's giving advice to her niece struggling with her children, reading to pull her hair out....
I don't feel everyone who hasn't experienced has nothing to offer though.... if they're sincerely trying to put themselves in the others shoes , that is..but yeah.. it can be misplaced..
How I would relate to that myself would be.. when others who always get pregnant VERY easily.. would try to tell me to relax -when I/we couldn't conceive.. I wanted to (mentally) punch some of them in the face..
I found it very frustrating.. they did not understand ...those were Pat answers...ya know...it wasn't this simple anyway.. turns out it was a medical thing, so no amount of relaxing was going to help me.. I needed to go under "the Knife"..
Those who encouraged me to seek help, get an Infertility work up...that was my answer.
If we can relate in small ways.. even if we didn't walk that particular journey ourselves..stay away from pat answers obviously... this has to help some ...