Please Write Me an Ending-Spoiler!

Rating: 2/10 (20 August 2018)

I have two master's degrees and am an avid movie-goer. I like the sci-fi thriller genre, but please help me understand this utterly confusing movie's ending. I waited patiently, hoping dystopia would be rescued by the "brilliant" science team of Krasinski & daughter. No such luck. At movie's conclusion, we see the family members wandering around outdoors, having figured out that dog-pitch electronic whistles and shotguns can subdue the alien critters. But for keeps? For a time? For real? Can someone please explain the outcome?