I usually dislike break-up stories, just as I usually dislike constantly fighting exes.
However, the break-up at the end of Death in Paradise, Season 3, is excellently written.
I'm conservative enough to not have the highest opinion of couples who divorce because they are bored or irritated. The statement, "My needs aren't being met" may be legitimate but sometimes, the needs are so entirely unrealistic that nobody would ever be able to meet them.
My annoyance at easy break-ups being stated, the split between Humphrey and his ex on Death in Paradise is a good example of how incompatibility actually can lead to a marriage falling apart.
Humphrey Goodman moves to St. Marie, believing that his wife will follow. She doesn't. She requests a divorce instead. However, she shows up a few months later, having discovered--as anyone with sense could have told her--that simply declaring a marriage over doesn't suddenly make life exciting and satisfying and fresh. Her world didn't become instantly magical, just because she shed the supposedly boring husband.
There's a fantastic scene at Catherine's bar where Humphrey orders a rum
drink, then encourages his ex to also order one. She takes one sip,
grimaces and sets it aside, requesting her usual gin & slim.
Humphrey then points out that with his move, he was trying to save their marriage--that's why he took the post to St. Marie in the first place. And it might have worked. It worked for Humphrey. He is fundamentally open to new experiences and the move expanded his horizons while shoring up his abilities as a leader. He absorbed it all, from classic mystery denouements ("That thing where you gather everyone together--I rather enjoyed that last time") to garish shirts to lizards to rum...
The point here is not that people have to like rum. In his unending search for decent tea, Poole never did.
The point is, the ex-wife wants both: she wants her unadventurous, yuppie, staid life back in England alongside FUN and ADVENTURE and CHANGE! This unlikely combination of needs is something Humphrey attempted to give her.
Except he no longer can. He has moved on--too far--while she didn't. He can't backtrack. He puts the gap between them down to individual growth (and to him being in love with Camille Bordey, though that is arguably a convenient emotional idea for him to hold onto). And the truth is, I rather think the ex-wife would have ended up bored in St. Marie. She carried her dissatisfaction with her. Nothing can cure that.