you can be an expert in every aspect of creo and still be a poor designer. just as writing is rewriting then design is redesign, there is nothing new in design today.
to improve your design skills i suggest that you start looking at old designs. go to a hardware store and look at all the different shelf assembly's, from different companies for example. look at the different products available today that you are interested in, copy them, modify them.
if possible the best way to learn to design is to start making things, assembling things and finding the good and the bad solutions that are out there.