This is a very important and vital issue. Actually, the concept of simplicity may vary from one person to the other, and you end up with many different points of view. I guess, however, there can be a consensus on the simplicity of Jean Claud Ellena's works. He employs few elements/notes in a creation. Likewise, there could be a consensus on Amouge Gold's (men's/women's) being complex because it has so many notes.
Linear is by no means simple, IMO. Black Oud is not a simple fragrance although it's somewhat linear. Solifolres can go into phases too, but that's because the central motif (flower or whatever) itself passes into changes. This needs a lot of elaboration. Good topic