I think that it is Imagination, to get what you see in  your head into your 3D Art and that is not easy.
I have seen Poser Users with over 2000 Imags in their Gallery and the last one still looks like the first one when they started BUT I also have seen Poser Users that have only 16 Images in their Gallery and the first one is as Fantastic as the last.

With some time it is easy to get to know a program fairly good but NO time in the World makes you creative if it is not in you.

Just my humble Opinion.