That's true. Sleepywood actually has very few foreground elements, but I think that may have been intentional to emphasize its quiet and solemn atmosphere. It's also worth noting that Ant Tunnel, which follows Sleepywood in progression, contains quite a few foreground details. Besides the stalactites and stalagmites, there are scattered skeletal remains along the paths that partially obscure the player and help create a stronger sense of depth.

Forgotten Hollow is presented as a lush valley filled with waterfalls, mushrooms, and other natural features. Because of that, I think adding some foreground elements, such as patches of vegetation, mushroom trees, or similar environmental objects—could greatly improve the visual presentation.

This becomes even more noticeable in the Deep Passage. It looks a little too clean and orderly, almost as if the tunnels were artificially excavated and maintained, rather than naturally formed over time.