Just my opinion of the matter but from what I've seen a lot of anti-natalist rhetoric is focused on how awful it is to be a SAHM by highlighting the unpleasant elements of reality like constant cleaning, exhaustion from a kid who doesnt sleep, a father/husband who doesnt do enough, making personal sacrifices for the sake of the kid, etc. They do this while also ignoring the countless positive elements or blanketing them under an empty platitude like "but I love my kid(s)"
While I don't plan on watching the movie or looking any further into it, I can see based on that trailer why people would get the impression of anti-natalism even if its not what the movie is about.