Jessica Lange as an Actress with Dementia

In “The Great Lillian Hall,” Jessica Lange plays a veteran theater actress — a legend of the Broadway stage — who is always putting on airs, reciting bits from her favorite roles, and carrying on in the tradition of fabled actresses who get known for playing characters like Blanche DuBois because they’ve actually got a lot of Blanche in them. (They believe their own illusions.)…