Conversely, couples who don’t fight have let the fire go out and are just living hollow lives.

I mean... there's a certain angle on that which is kinda-sorta true. Human interactions create conflict and its not abnormal for couples to argue or show resentment towards one another for different reasons. Its not good, but it also isn't strictly unhealthy either. On the flip side, couples that are either incidentally or deliberately avoiding one another tend to be in relationships on the decline. So I can see "fewer fights" because you're literally just hiding from one another (either physically or emotionally) as a really bad sign for long term marital health.

But fighting with your SO is also often a sign that you're both under a lot of stress. I wouldn't even say that's problematizing relationships with partners so much as it seems to breeze by why the couple feels under the gun all the damned time.