A Masterpiece This movie is a PERFECT example of how to build tension. It's slow, it's subtle, it worms it's way into your mind and creates a genuine sense of safety and security. For the first hour, you might even forget you're watching a horror movie. But then, oooooooh but then. I don't want to give a single thing away, but once the story takes a turn, there's an exponentially building sense of dread that doesn't ever go away. Again, it starts off gradual, but ramps up exponentially, until dread turns to fear, turns to horror.
Alien is an effective horror movie not because Xenomorphs are scary by themselves, but rather because they pose a real, tangible, threat to characters that WE care about. Characters that we have a chance to really understand, and grow familiar with, even fond of. So when horrible things happen to them, we're invested not because of the shock value or the jump scare, but because WE don't want them to get hurt. It seems that most "horror fans" have forgotten that.
Pacing and writing aside, the film is absolutely gorgeous. Even in the first 10-15 minutes, when scenes take place in normal apartments and bars, there is some really fascinating cinematography at play, and once it gets to Sweden, every shot is breathtaking. The use of symmetry and color is reminiscent of Kubrick, and I mean that as the highest compliment.
The score is fairly understated, as it was in Hereditary, and I think it works even better here than it did there. It's only purpose is to build tension, instill dread. You won't even notice it in the background of most scenes, and often there's actually nothing to notice, but regardless of whether it's completely silent or blaring violins, it always feels appropriate.
Look, I love big, loud, dumb, gory horror movies as much as anyone. Give me over-the-top violence and a paper thin plot, and as long as things keep moving, I'm along for the ride. But I can also appreciate auteur cinema, where a single artist's vision is realized by thousands of actors, camera workers, set designers, etc. And this is exactly that. Anyone who doesn't like the movie, I won't tell you you're wrong. But I'd ask that you at least try to appreciate the work that went into it, on literally every level.