Now, the aliens are certainly intelligent enough to use tools — they just don’t need them. Evolution has given them everything they need to kill just about anything they want to. They can gestate inside any host, taking on whatever physical characteristics of that host are needed to survive in a new environment. Their bodies make their armor, their secretions make their architecture. Technology is irrelevant. Their biology is so perfect that they are technology. (I’m partial to the theory that the derelict spacecraft discovered in Alien and again in Aliens was carrying the alien’s eggs to use as bombs; Burke and the Weyland-Yutani corporation want to exploit their biology in much the same way. It’s all IP to humans!)
The climactic scene in Aliens is obviously Ripley’s battle with the alien queen. Exoskeleton to carapace, blowtorch to hidden extra jaw, it’s literally a battle between a human plus technology and a biologically superior lifeform. Again, I love how low-tech Ripley’s suit actually is: it could easily have existed in 1986, but probably never will, if Amazon’s warehouse robots are any indication of our future. But I also love that Ripley wins not just because she can put on the suit and know how to use it, but because she can take it off.
Think about it: all Ripley is really doing inside the exoskeleton is holding off the queen while she is opening the airlock. Even with the benefit of a robotic prosthesis, a human being can’t kill the alien: only space can. Ripley and the queen tumble head over head into the bottom of the airlock. Ripley luckily lands on top, but is also able to ditch her techno-suit and climb out of harm’s way. The alien queen can’t even break off from her egg sac as quickly as Ripley scrambles out of her suit; she’s too tied to her own biology to let any of it go, to treat it as something other than herself.