Cinematic story telling of any kind requires a compelling plot, characters with depth, and the judicious use of symbols. Horror films often under develop all three areas, falling back on jump scares and simple gore. I am sorry to say that in spite of its thinking-man's art film approach, "Us" is a basic slasher film lost in its own fun house.
While the premise of the plot and twist is interesting, the story telling is overwhelmed by a massive heaping of symbols borrowed from a variety of cultural genres ranging from classic arts to Americana. Unfortunately, the symbols taken together dont communicate a cohesive narrative. Ballet, bunnies, a chain of humans and humans in chains, mirrors, exits, beaches, masks, and diabolical clones - the director applies a mash of symbolic language until the use of symbols is the main ingredient and the violence is a confusion of unsurprising assaults while the flames of horror are doused by extinguisher of the ridiculous.
In this film, the Apocalypse is the release of symbols to free range across the cinematic landscape without restraint. In that regard, the film really is horrific.