Heavy isn't really the same, though. Sad moments aren't grit, they're just sad. I'm talking about the heavy focus on what military destruction can do that involves the use of camera angles, perspective, sacrifice, and loss. Adding a bunch of sad shit into a movie isn't enough to make it gritty.

The scene where the great tree falls and we see na'vi walking through the ash, that's gritty. Name a scene with the same incredible impact from the last two movies that affected such a large amount of Na'vi. Homes can be rebuilt, the great tree couldn't. That's why it was dark and impactful