What kills love is rarely one large unresolved ‘thing’ but years and years of small resentments.
Very true. From the male side, the small resentments usually build up due to nagging and sexual denial. Unfortunately, most women have had it drilled into their heads that if you are making any effort to keep sex regular, you're being exploited and mistreated. The man should do what the woman wants because duh, that's just what a good partner does, and the woman should not do anything the man wants because duh, a good partner wouldn't ask anything of you. What women want is just objectively correct, while what men want is disgusting. Therefore the solution is for the man to align with the woman.
e.g.
I know a lot of women who are staring down middle age with husbands who haven’t really altered how they operate at all despite children, leaving the wife doing a full time job and all the housework
Is this "all the housework that is required to stop us from dying of black mold and vermin-borne plague," or is it "all the housework so that the state of the domicile pleases the woman?"
Because IME it's always the latter. However, the gap is that a woman's desire to see dust-free shelves doesn't hit the same reward center that a man's desire to watch a Peter O'Toole movie hits. So the woman thinks of housework as being an objective need, like the need to consume enough calories in a day to not die. The man does not. Prior to the woman entering his life, the man lived in a significantly less-houseworked state, and if she walks out? All that housework that the woman insisted NEEDS to be done...won't done. Because it's not an objective human need, it's a woman's psychological need. The exact amount of housework that
needs to be done will get done, as evidenced by how few divorced men die of an insufficiently clean house.
The man then perceives this situation as, "You do what I want, and return you get none of what you want--I will merely make less of an effort to induce misery in you." If I mop the kitchen floor more often, I'm not getting a handjob. I'm getting nagged less. If I perfectly please the woman in every way, this doesn't result in a regularly scheduled, private, 1 on 1 Saturday Night Lingerie Show. It means I get to the zero state. The woman is now happy, and I am simply not-nagged.
And I don't think this is quite what you had in mind, but indeed, the housework issue does in fact result in quiet resentments building up over years. He perhaps makes an effort to please the woman now and then, but these efforts never end with anybody naked, so he loses interest, and there is never lasting change. The woman can't figure out what is going on, is certain that any solution that involves her naked is yucky, and concludes that she isn't working hard enough at making the man miserable.