No no no, you misunderstand. You're absolutely FINE on The Lake Guardians' composition. Look:
The boat in the foreground is eventual the center of attention, the vertical sword, parallel to the edge of the picture, leads the eye up, and every element successfully leads the eye around the picture without being stupidly pointed. True, it's flat and somewhat stiff, but it's well composed. Now compare that with the cave one:
THe eye starts at the cave entrance (the darkest point), the linear elements lead the eye to the right (over the bell and sarcophagus), and points the eye up to the light (the brightest point). This is fine, but the eye gets stuck going from POINT A to POINT B, there needs to be more elements to lead the eye BACK in a circular continuation, or the composition just "doesn't work".