It seems strange that Prometheus appears to have more impressive technology than 1979s original Alien, but this actually does make sense within the franchises fictional reality. The Alien timeline is a little messy thanks to the franchises contradictory canon. Alien Vs Predator offers one version of the Weyland-Yutani Corporations history, while Prometheus retcons this with an entirely new story. Even within the Alien movies themselves, discounting the Alien Vs Predator spinoffs, there are some confusing irregularities. Aliens upcoming TV show Alien: Earth may justify some of these plot holes, but others can be excused by viewers.
https://screenrant.com/alien-1979-technology-gap-prequel-movies-make-sense/