The introduction includes a 1-page essay about the state of design in 1991, which is shockingly clear.
At that time designers, for the first time in history, had access to all of design's history. Clever design, especially graphic design, usually comes in the form of recontextualizing what has been done before. All of a sudden the references everyone was paying attention to, the current market of design, was exploded to include all of history's worth of references. They didn't know how to tastefully dip into everything cohesively, so the designer's argument is something like history won't remember 1991 because those designers were learning how to cope with their overwhelming possibilities.