And to think there was even more (and worse) of that stuff that did not make it to theatres.
Corporate history is like anything else, it's written by the victors. In this case, The Black Cauldron was green lit by the previous board at Disney, and when Eisner and Katzenberg came on board and it failed it was not their fault or problem to worry about any more.
By the time the movie was released to video in August 1998, the Disney forumla for film making was set in stone by all the features leading up to Mulan, as well as imitators like Anastasia. In contrast, The Black Cauldron has no celebrity voices (unless you count John Hurt), no songs and is intentionally scary and ugly at times. It's little wonder why millennials obbsessed with Ariel, Simba and Genie didn't go for it.