After leaving an abusive relationship that lasted many years, I've become far less tolerant of (unrealistic) toxic relationships in the books I read. When these characters have relationships that somehow "work" ... it's usually because the reactions of their friends and partner are based on (all too common) false beliefs about human emotions, attraction, and resilience.
I know that the reason I stayed in that abusive relationship was because I believed that my natural, honest reactions to my partner's behavior were somehow "wrong" and therefore shouldn't be allowed to exist. I essentially erased myself and the truth of how I felt for the sake of the story I wanted to create with that relationship. I tried to live the fiction and believe the alternate reality version of events was true.
This resulted in my partner being perfectly content increasing and refining their bad behavior until I broke so completely that my only choices were becoming just as bad, dying, or leaving.
But in fiction, the characters don't need to shatter and twist themselves into knots around a world view that destroys their emotional stability (the way they would in reality). Wanting the happy ever after wins over all. So when the author portrays the relationship as okay, readers often overlook the hand waving that makes the magic happen.
If a reader isn't sensitized to the real damage of the beliefs beneath the surface that allow a real life person to appear comfortable with abuse, it's easier to accept that a happy ever after is possible in that scenario. We haven't progressed that far from an era when keeping silent for the sake of reputation was one of the only socially acceptable solutions to partner abuse, after all. The myth that people can be fine in that type of situation made it easier to see it happen and turn away.
Toxic people can be written well and move through story arcs that bring them to a point where they are no longer destructive, but it takes a solid understanding of how humans function. Watching someone go through the shock of realizing where they've gone wrong, recognizing the damage they've caused, and doing the work of changing is a very interesting story, so I can see the appeal.
I just have too much experience of the fake version of that arc to trust the hand waving. I need to see the realistic steps of change and actual-human reactions of the people around them to even begin to be comfortable with the "toxic character" arc these days.