The technology of Alien appears to be near future, ie not radically different from our own, the implication being that it's only a few decade ahead of us, which I could live with.
... but the nature of their flight is such that they imply widespread and very distant use of space flight, which is clearly relatively routine, which to my mind implies far more than a few decades, probably a century or more (and I seem to recall from somewhere, probably one of the trailers, seeing 2085 mentioned for Prometheus, implying a lot later for Alien).
I'd think that the technology of that time scale would be so far advanced from us, and to be almost impossible to comprehend, although obviously that wouldn't do for a film which we're trying to watch. Even an old clunker of a ship used by a second line company (which the implications of "The Company" tends to exclude) would still be using at least some technology which would be far more advanced.
You tend to see this more in written science fiction, than you do in Hollywood science fiction, because the average audience wouldn't be able to deal with it, and for that matter, you'd spend too much of any film trying to detail the background!
I'm thinking of stuff like advanced nano-tech, and AI that actually works and exists (or is at least indistinguishable from real AI if that turns out to be impossible). Of course, history has shown that we generally aren't very good at predicting the future, because something unpredictable which radically changes things will come along, but there future is more like a couple of decades from now, only with some sort of very advanced space flight, which is apparently totally independent of any other technological advance.