That's a very fair appraisal of the situation and I agree. I'm sure no one has seriously addressed the Alien's origin until Scott and Co. First tackled the notion when 'Prometheus' was first called 'ALIEN: Origins'. Then, of course, a lot of things changed. They always do. Then they get recycled, like the reappearance of the pyramid concept from the early 'ALIEN' scripts turns up again in 'Prometheus'.
In this regard, I sometimes think 'Prometheus' resembles what 'ALIEN' could have been
had such elements been included.
Humans were always scheduled for a dose of black goo at a specific point of development. We were never meant to be left to our own devices and develop space travel.
I think this statement is the key to everything this series represents. My own pet theory is that the Derelict didn't
crash on Acheron. It was deliberately placed
there. As a bait in the form of a warning, set to trap Humans once we became a space faring species. The derelict may turn out to be the Galaxy's great mouse trap, set to eradicate out of control vermin. Namely, Us.
Kind of like the inverse of the monolith found on the Moon during the events depicted in '2001 - A Space Odyssey'. Except the purpose of the derelict is much more malign and it was intended to keep us away from that particular region of space - or suffer the consequences for ignoring the 'warning' message.
I really like what Scott is doing here. I found 'Prometheus' to be a very uneven movie, but it laid the foundation for an extremely intriguing premise that I am happy to watch unfold during the next few years. I suspect this is going to be a very exciting time to be an 'ALIEN' fan.