MEXICO CITY—Isaac Lee, a top executive at Mexican broadcaster Grupo Televisa SAB, says he stays up at night worrying about people like Alicia Torres, the 83-year-old matriarch of a large TV viewing family. Once a dedicated fan of Televisa’s prime-time soap operas called telenovelas, she is now hooked on Netflix.

“Telenovelas became overly repetitive: I love you, you love me, you betrayed me, and they lived happily ever after,” said Ms. Torres. She said she doesn’t think the people in her family—eight children and 19 grandchildren—“bother...