As someone who worked a lot in realistic VFX I concur with the observation that nearly no game is doing tone mapping right and my guess to why that is always has been the fact that doing it right is just very complex.

There are many, many things artists need to do correctly, many of which have no idea of the whole pipeline. Let's say someone creates a scene with a tree in it. What is the correct brightness, saturation and gamma of that trees texture? And if that isn't correct, how could the lighting artist correctly set the light? And if the texture and the light is wrong the correct tone lmap will look like shit.

My experience is that you need to do everything right for a good tonemap to look realistically, and that means working like a scientist and having an idea of the underlying physical formulae and the way it has been implemented digitally. And that is sadly something not many productions appear to pull off. But if you pull it off everything pops into place.

The added complication with games is of course that you can't just oprimize the light for one money shot, it needs to look good from all directions. And that means it is hard to make it look as good as a film shot, because that risks making it look like crap from other directions which studios aren't willing to risk.

The dragon in The Hobbit isn't just about the tonemapping, it is at least as much (if not more so) a lighting issue. But the two can influence each other in a bad way.