A faithful adaptation
can be unplayable (in the "
shouldn't be played" sense, not in the "bad rules" sense) if the original contains outdated or bigoted tropes.
Sometimes, fixing those tropes means rewriting things to the point that an adaptation can't be faithful--like with 5e Ravenloft, which
@Micah Sweet doesn't like. I believe that a lot of Ravenloft's tropes
were so outdated or bigoted that the only way to fix them was to completely rewrite large sections of the setting. And Micah
has been saying that, in their opinion, settings
shouldn't be adapted to 5e if they have to be changed so much they don't continue with the old lore--that they should be left unchanged, even if it means nobody will ever play them again.