Agreed; kinda like my SW gripe, there’s a lot about the Alien’s universe (the structure of Earth’s government[s], their relationships with corporations like W-Y, what advances in sciences like planetology might make LV-426 prime real estate, etc) that we don’t know that might very well make certain “plot holes” non-issues.
It’s been a long time since I read the novel, but IIRC, either Dallas, Kane, or Lambert turned off the alien ship’s distress beacon. So there’s no signal to warn potential colonists or other ships. But this is not supported on-screen, so did no one else ever pick up the alien ship’s distress signal?
Let’s assume that, after the Nostromo was declared overdue, then missing, that the original Nostromo conspirators at W-Y wiped the computers to cover their back trail and wrote off the “Xenomorph Project” as too dangerous. They retire, then maybe die of old age, etc.
In the mean time, the original LV-426 crash site is partially buried under a rock slide (supported by the extended edition/director’s cut), and missed on the planetary survey before the terraforming colony is established. It’s feasible the rock slide damaged the alien ship’s transmitter, and, since we don’t know when that rock slide occured, it’s feasible that the planetary survey didn’t see the ship and/or pick up the alien ship’s distress/warning signal
Ripley shows up 5 decades later, with an incredible story. No one wants to believe her. After all, there’s no real evidence to back her up, and no one on LV-426 has seen a single hint of what she’s obviously raving about. But Burke, being the slimy weasel that he is, decides it’s worth a look. Instead of asking for/sending a fully equipped and trained Xeno-contact team, he sends a routine memo to have someone on LV-426 check out a set of coordinates.
Hilarity ensues.
The real problem is this: did no one on LV-426 send out a distress call when things started going pear-shaped? (After Newt’s dad came back with a face-hugger, torso’s started getting all 'splodey, nasty xeno’s are running around snatching people up, etc).
If they did, is it feasible/plausible that Burke managed to quash that communique when it came into W-Y’s communication’s center? Did he pay off the duty techs in the Comm Center to ignore what they saw heard? Did they even see the message? Or did they just see the recipient’s name (Burke) and forward it without reading it? Would scared/panicked colonists send the message just to Burke’s attention, or do a “Send To ALL” distress message?
Or did things go so bad so quick that no one on LV-426 got a message out at all? I would find this difficult to believe.
The human portion of the Alien-verse does seem to be a partially dystopian, corporate-ruled-crap-sack, where corporate weasels are always trying to do stuff on the cheap, like sending “crew expendable” space-truckers to make first contact with a potentially hostile species. Or making military transports partially automated to cut down on crew costs/overhead.