What does Hereditary have to say about literally anything? 

Does it comment on grief?
Not really. We’re introduced to Annie who wears this guilt that the passing away of her mother isn’t as grieving as she expected or maybe even wanted it to be.
Does it say anything about dysfunctional family dynamics— a disregard for healthy display of emotion?
Not really. We’re shown that these characters bury their emotions and even punish others (and themselves) for being emotionally honest, but it couldn’t be bothered to expound on it because it’s more concerned with playing to it’s genre.
Are we given any reason Annie wears guilt or that she “adds stress” to her family? 
Other than feeling the way she does about her mother, we’re given none whatsoever.

So what is Hereditary? An indulgent genre piece that’s not only missing an hour of family drama that would emotionally tie things together (as confessed by the director), it’s spiritually empty. For all it’s comparison to “The Exorcist”, Ari Aster’s first film pales in comparison. William Friedkin first of all never set out to make his film a “horror”. We’re met with a mystery of how things come to be and one priest’s crisis of faith. Hereditary is as depthfully honest as a tack compared to a sword.