Was Melissa Mathison a hack writer?
She's been accused of plagiarizing an unproduced script titled The Alien written by Satyajit Ray in 1967. And among the 10 works that she that she wrote, only ET was an original screenplay.
https://www.nytimes.com/1983/05/25/movies/writer-loses-a-round-in-lawsuit-over-et.html
The Black Stallion - adaptation of a book
ET - original screenplay
The Escape Artist - adaptation of a book
The Twilight Zone Movie - adaptation of an earlier episode of the series
Son of the Morning Star - based on real events
The Indian in the Cupboard - adaptation of a book
Kundun - based on real events
The Emperor's New Clothes: An All-Star Illustrated Retelling of the Classic Fairy Tale - sequel
Ponyo - wrote the English script for the Japanese film
The BFG - adaptation of a book
https://www.telegraph.co.uk/films/2016/07/21/melissa-mathison-the-life-and-death-of-spielbergs-right-hand-wom/
https://www.reddit.com/r/movies/comments/gyckmi/i_watched_et_again_recently_its_a_great_film_for/