I think I would have been happier without the ending, in terms of FL's actions/flashback, though at least the drama didn't try to peddle some sob story, and in the end post divorce there was an acknowledgment by FL herself, without "both siding", false morale equivalence or self serving cynicism.

Quite different from their previous encounter where she was absolutely atrocious, and overall much better than what we actually get from shown ranked higher than this, so in the "non sociopathic" scale this is not as low as one could imagine.

I don't think I would say the drama was nihilistically trying to communicate "this is a part of what love life is also like", that's not honesty, that's self serving cynicism (and also, it wouldn't be "love life" if there was no "love" and it was all a hypocritical facade), i.e. pretending that people are actually much worse and more sociopathic than they actually are. I don't think that this is the case, nor that the drama was trying to provide some kind of nihilistic take about the "facade" of happy families.

Happy families do exist, decent people do exist, and the ones putting up a "facade" while really being self serving monsters are definitely not most people: this is just nihilistic and self serving cynicism, and I don't think that the drama was trying to push that as a narrative. I would go one step further and say that the drama was not nihilistic, despite what happens in the plot.