Until Issa Rae and John Cho announced “Harriet” star Cynthia Erivo as a nominee for best actress for the 92nd Academy Awards, it was looking increasingly likely that the Oscars were heading for a repeat of the #OscarsSoWhite controversy that drove the Academy of Motion Picture Arts and Sciences four years ago to aggressively begin diversifying its membership. Instead, Erivo saved the Academy from the embarrassment of yet another slate of all-white acting nominees — but just barely. This year’s Oscar nominations for acting still managed to shut out a wealth of highly regarded performances by actors of color who...