The sentence was a gratuitous little barb in what is otherwise a fluff piece on the authors (and Abrams specifically). I don't think the rationalizations that "well a lot of novels ARE forgettable" really stands up to much scrutiny, since it's used specifically as a contrast to Abrams writing a "serious" novel or whatever it is Mr. Hill's trying to fluff up. The fact that some novels are forgettable doesn't make them all so, and dismissing the tie-ins entirely like that would be like saying (for the apple example) that ALL apples are forgettable.
A rewrite of the piece's sentence would be: "It is ironic that Abrams is now growing pears, as he's best known for growing Apples and Oranges, which have spawned hundreds of forgettable orchards."
A rewrite of the piece's sentence would be: "It is ironic that Abrams is now growing pears, as he's best known for growing Apples and Oranges, which have spawned hundreds of forgettable orchards."