The point is, creativity is defined by its bounds. It is also limited by its bounds. For an artist, it might be funding, what space you can get hold of and how to stay alive in your freezing studio, but that is an influence on the work produced. An architect deals with an assortment of complexities that all have to work together: resource consent, building consent, will the thing stand (if it will stand in an earthquake is another matter) and, quite importantly, with all that in mind does the building still work?
The characters in Inception are stuck in a place where the creative bounds are stretched. The architect has full control over the environment. A forgery expert is like an extremist actor turned identity thief that can become the person he is acting. People can battle without gravity. There's even an avant-garde pharmacologist.
Infinite creativity, stretching back to the creative psychological theories of Jung, is both a theme and an ongoing movement. The movie itself has spurred a lot of thought. Graphic designers have made countless infographics to try to untangle the mental knot that is left after watching it (possibly a few times). Memes have sprung up and it seems to have become a common reference for whenever something is within something else or not knowing how you got to certain places.