Oliver Farry at New Statesman asks the question, and Adaptation is one of the films he looks to for answers.
I would point out that "good" isn't the same as "accurate." Nobody wants to see a film about a guy dicking around on Facebook, staring at a blinking cursor while his leg jiggles up and down with ever-increasing speed, watching a lot of TV, reading about writers who are actually writing, and saying "I suck, I have made a horrible life choice" every five minutes, while a clock ticks very loudly in the background and his hair turns grey.
But enough about me.
The screenwriting credits for Adaptation are shared by the two brothers, making Donald Kaufman, along with the Coen brothers’ editor Roderick Jaynes one of the few fictional people to be nominated for an Oscar. It is also one of the few instances where real-life authors have been integrated into the meta-textual fabric of a film (Guillaume Nicloux’s 2014 mockumentary The Kidnapping of Michel Houellebecq is another). One imagines the rarity of this happening is less due to reticence on the part of authors than the fact that most writers are simply not recognisable enough for the conceit to be fully effective. (Source)