We've discussed this at length in other threads, but briefly - it made no sense to the Alien franchise that Aliens were present in the present day - and making that film prevented a possible Predator III film without mixing the franchises together. What is done is done.
By the way, I was under the impression that it was Ridley Scott's brother-in-law directing this film. His name is only there to give it more credence.
I would really like to know about the 'Space Jockey' alien found on LV426. That is something people have wondered about since the first film was released. But how can the origin of the Aliens now square with what happened in AvP and AvP2? I will make no sense.
Sorry, I think I deserve enough respect from film-makers that they can keep some continuity within the fictional Universes that they themselves have created. If they can't do that, and actually watch the previous films they have produced, they why should I bother to watch them either.