Hereditary was first a movie about grief and family dysfunction before it displayed its bone-chilling supernatural horror. That's why it worked so well with the audience. The slow burn pace really took it time to establish the characters' position in the story. It's already a great movie before the spooky part came in, which you don't catch a lot in the horror movie nowadays.
Anyone who has seen the movie would find themselves reliving it silently; during the drive home, gazing at the endless rows of honking cars, your everyday view now seen from a whole new light. They would find themselves staring into empty space thinking about Alek and Sari, a sincere reminder that there will always be a fleeting moment of joy and love amidst the choking haze of Jakarta.