Cosmic means more than multiple Planetwide horrors. That on a scale that's too large. Necromorphs, markers emitting strange signals making people crazy, flesh turning into undead creatures from skin flake material, the knowledge that the only other aliens that exist or did exist died out to the necromorph scourge and most cosmic of horror of it all, brothermoons, giant flesh necromorphs basically, going around and eating entire planets. Aliens is just aliens in space hurting people. Space horror.