It's not suspenseful to YOU. Therefore it doesn't work for YOU. But it works for ME and other fans of the film. I'm not quite sure what you mean by the build up being 'obvious', either. The way I see it the build up is either effective or it isn't, and I think most would agree that it at least is. It establishes the characters, the mood and the undercurrent of distrust amongst certain characters.
I'm not sure why you even felt the need to ask this question, tbh.
Lol, you talk about how the build up in Aliens is 'by the numbers' yet you won't even acknowledge how by the numbers it was for the screenwriters to attempt to make the alien more of a threat than it needed to be at that point in the film.