As far back as the mid-1980's, American producers were playing this game. TV shows of the era typically featured a White male lead with a woman and a Black sidekick. Matlock is illustrative, but I distinctly remember a satirical show making fun of the new season, describing each new show, and including the boilerplate "...with a woman and Black to help him." At about the same time, in No Way Out, Kevin Costner's best friend was wheelchair-bound and Sean Young's best friend was Black.

What has changed is the number of groups that need to be included lest the dreaded cancel-call be issued. Not every show must have every category, but in any series with any pretension to long-term survival, there will of course be major characters who are Black and/or female, but there will also be an Hispanic, an Asian, a mixed-race couple, a gay couple with kids, a "differently abled" person (all too often a cloyingly cute Downs child), a trans person and a non-binary person.

As Fildy notes, these things are much harder to do in an adaptation without doing violence to the source. But the makers of many adaptations may not feel much loyalty to the source, which they use only to suggest a plot and perhaps to let them bask in some reflected, if dishonest, marketing glow. Jane Austen's books often escape mutilation, perhaps because so many of her characters are female, and perhaps because so many of the White people in them, especially the men, are so dreadful or foolish. With some fantasy works, whose fans demand faithful recreation, the trick is more difficult; the producer may have to restore order to the universe by making some other film devoted entirely to establishing his (it is usually his) diversity bona fides.

It’s important to remember that we the audience are not entitled to a faithful film version of Wuthering Heights, which, unlike, say, a Michael Crichton "novel," was always just a book and not a movie treatment masquerading as one. If one thinks of the adaptation of an old book as first and foremost a way to create jobs for a diverse array of people and to give a diverse array of people the chance to see "themselves" on the big screen, the faithfulness of the adaptation simply does not matter. The thing works on its own terms, or it doesn't. If the movie distorts the book, the book is right there to read, in most cases exactly as the author wrote it.