I suppose that model works if one person wronged the other, or if one was clearly at fault.
A lot of times, the relationship ends because both people outgrew it. It is unfortunate, but it happens. And usually, the case for getting together in a romantic relationship usually stems from genuinely liking that person first. When you realize that as a romantic couple it no longer works, you don’t start magically “not liking” that person. It just means the romance isn’t there. It also means the prospect of a romantic relationship with that person is closed. It is sometimes sad, but not a case for animosity. And when a relationship ends that way, neither person goes from being a loving spouse/significant other to some rando off the street you want nothing to do with.
Of course the flip side of that is if you find out, into the relationship or marriage, the person isn’t the person they presented as, or otherwise wronged or deceived you, there is no reason to keep up a relationship with that person. Of course, the Hollywood story of that is a person who spends the rest of their lives on a vendetta, which is completely destructive. In this scenario, excising that person from your life is perfectly fine.
I personally am remarried.
With my first marriage we married young, realized not too far in that we had outgrown each other, and parted amicably. My ex wife is a perfectly nice person; she has remarried (as have I, eight years later) and we do keep in touch. Had we not become a romantic item, I am sure we would still be friends. When people express surprise at this, I say “My ex wife has done nothing wrong. The only thing she is guilty of is having been married to me.”
If tragedy befell my ex wife, I would be sad, if good fortune befell her, I would be happy.
Truth be known I have a pretty good friendship with most of my ex girlfriends. Luckily, I have never been egregiously wronged, nor have I egregiously wronged anybody to the best of my knowledge.