Yes, constant complaining or whining from an adult is a downer. And as a women who stuck out a horrible first marriage for 13 years before I really "got it" that I had to find a way to leave for my daughter's and my own emotional health, I can also attest to the difficulty of actually making a change – especially a big one that will have familial and finanacial repercussions.
I'm sure grateful for my girlfriend and a sister who very kindly received my anguished tales, each a version of the story they had witnessed for years. They both were wise enough not to lecture me on how to change. They both gave me the most helpful feedback when they said things like, "That must be intolerable. You are reaching the end of your rope, aren't you? What do you think you can do about it?"
I am NOT "the type who is not content to be discontented with circumstances." (Wow, how's that for a confusing set of double negatives?) I've been watching people closely for my whole sixty-some years, and nearly everybody (including me!) secretly believes other people do, or at least ought to, understand things the way they do. But we don't – we are vastly individual with very different personalities and inclinations. We approach similar problems in very different ways.
I had a conversation with a "friend" just yesterday who has several times expressed severe judgments against women who stay in abusive relationships. He was surprised when I shared with him how long I stuck out my first marriage, and my many "good" reasons for doing so, religious, cultural, familial, financial, and emotional. It had never occurred to him that it's not an easy choice for other people to change.
And yet, he's sticking out a job he detests, and drinks and games a lot to ease his form of emotional death. It doesn't look to me like his choice not to change his employment is all that different than my choice to remain in a marriage that I kept hoping would reap rewards eventually.
Did we both put ourselves intentionally into those situations? Yep. And did they turn out as we perhaps reasonably hoped or expected? Nope. I don't think many of us have access to a clear vision of how different choices will affect us in the long run.
What's there to do for it? Not a whole lot, I suspect, other than to keep learning as we go. We all do what we do until we can't do it any more, and the tipping point for each of us, in each situation, is unique.