You mean like, "if the monsters hunt by sound, why aren't they constantly just attacking the waterfall all the time" (which is something I have seen people wonder about online)? I think the answer to that (and a lot of other nit-picks about the movie) is pretty self-evident; the monsters must've tried attacking the waterfall when they first encountered it, then realized that the sound didn't represent a sentinent creature, and then were intelligent to learn to ignore that particular sound from them on (and thank God that they did, because that would be a much lamer movie if they were that dumb, haha).
More like “if these monsters hunt by sound, why are they so conveniently terrible at hearing?” or “why do they have to expose their weakness every time they need to hear? Can they not hear at all when their armored up?”Compare their abilities to ANY creature that has this ability and the issues become numerous. Then there’s the human element...
If these creatures hunt by sound...
... why not live near the waterfall, which they conveniently ignore?
... why bring a baby into this world when you will clearly have a finite oxygen tank level and they WILL cry?
... why did people never try to hurt the creatures with sounds before?
... Does no one in the house snore, fart, burp, sneeze, back crack, defecate or any of the multitude of involuntary noises our body makes which are louder than the noises that seemingly draw the creatures?
Etc forever. Because the premise doesn’t make logical sense at all. The film works because it makes dramatic and emotional sense and because it is extremely well made. Like Hereditary.