"The ending is sad."
Translation:Slutet är sorgligt.
Yes, exactly. ledsen is a feeling experienced by someone. Filmen var sorglig, jag blev ledsen 'The movie was sad, I got sad'. – It works the other way around too, if you say a person is sorglig, that will not be ambiguous as with sad, it will only mean that they are sad as in pitiable, not as in feeling sad.