i think there are two separate issues here.
firstly, the execution of the shot.
secondly, how the shot is viewed by the viewer.
a shot can be simply executed but look complicated.
just as a shot that is painstakingly executed can look simple.
to me, i look for simplicity in the image, irregardless of how easy or difficult it was to take the shot.
in this instance, both the execution and the look of the image are complex.
why do i say that?
for a start, executing a 15 second exposure is not a trivial matter of merely pointing and shooting, but involves shooting in manual mode, with a camera that allows you to do so. further tweaking of the contrast was also required. a "simple" shot for me would be to point and shoot, and use the image straight out of the camera.
secondly, the image itself looks complex, involving several different colours and forms.
would be interested to hear your further views on this.