I think its all down to change of plan again....
We need to look at the Evolution of the Franchise from a Prequel Stand point.
Alien: Engineers.... Began to show us the Space Jockey was the Engineer Race who genetically Engineered Mankind using some Organism that allowed them to spread their DNA.... the Protagonist who discovered clues in various Ancient Cultures pointing to a Star System... that when they arrive they find is no a invitation and its not a welcoming place for our creators...
It is found at this point to be a place these Engineers had been experimenting on other Organisms (maybe using their Creation Tool the Nano Scarabs) and this Outpost is a place these Engineers have been working on many different versions of some Horrid Alien Bio-Weapon. Which they had intended to use on Earth. Hinting at because of maybe something we had done to upset them.
It was a movie that was set on LV-426 featured different Face Huggers, different Alien Organisms 3-4 different ones and crew being attacked and killed by them. The money shot was the Juggernaught taking off but crashing with a Chest Busted Engineer and resulting Ultramorph....
It was a tease at maybe being Alien and LV-426 a more direct Prequel... (but maybe Red Herring).. it ended with the remaining protagonist discovering this place is not the Engineers homeworld but Paradise was and this is where She and David would be off.... but its left open to if they go.
Prometheus came in off another draft and was aimed at the rather interesting concept on the Engineers, who was they and there role in the Galaxy and Creation and the stance that the Xenomorph as a experiment that was either the result of experiments on the now (Black Goo) or lead to them. It was cutting down the Xeno-elements but to give clues that this Place which is now a near by Moon LV-223 was still being used for the same purpose as Alien: Engineers.. which was to Engineer, Test and Produce Bio-logical Warfare and the Xenomorph was one part of that....
They gave us clues to the Xeno being viewed in some high esteam for the Engineers and its Origin or Creation is connected by the Black Goo.... where we was shown just 3 elements of what it can do.... and so fans only got to see the Hammerpede kill Milburn... Hybrid Human (looked like Toxic Avenger) kill most of the other crew.... at this point there was not much Xeno DNA and no Xenomorphs.... Then we see Shaw is infected with the Black Goo to then produce the Proto-Face Hugger which instead of a Xeno that killed a few people... it mearly was used to infect the Engineer at the end to Produce the Deacon which was the Money shot to bring home indeed this place is connected to the Xenomorph creation.
The Deacon did not kill no one, the Hammerpede only one, and it was the Engineer and Mutated Human Fifield that did the killing... i think this led to disappointment to fans.
It removed the need to see Xenomorphs, but via the Mural and how the Black Goo worked showed us how they would have came to be... but it was to vague..... they concentrated more on the Engineer and Mythos and Religious undertones a bit more.
Prometheus 2 was a work in progress, Ridley had mentioned it, then it went dark, then he would mention it again and it would go dark.... for the next 18 months after Prometheus, he would hammer home that a Sequel would step further away from Alien and LV-223 as far as the basis of this place being a place they (Engineers) conducted experiments to create horific Bio-Weapons.... The movie instead would be about Shaw and David and going to Paradise to find out answers, like Why was we created, Why was we to be destroyed, why did they create that Place LV-223 and if the Engineers are not God then who is pulling the strings at the top... it would likely had mentioned the Xenomorph and LV-223 but only in limited way.
Ridley had connected these Engineers are Fallen Angels and touched upon light connections to Paradise Lost Plot.. loosely.
This was a bold plot to do justice and i am sure a sticking point hence all the re-writes but it was to open a Franchise Direction where Prometheus offered us a Fork in the Road.
Fork One ==> Experiments and events in past ==> LV-426
Fork Two ==> Offer to explore the Engineers and history and culture and what changed a seeming Benevolent Planet Seeding Race into a Warmongering Bio-Weapon Touting angry Race.
But with Alien 5 information released and fans getting high hopes for this, as opposed to a Prometheus 2 to follow Shaw and her quest for answers that may end up showing us less of the Xeno Origins than even Prometheus did... just never sat well with a lot of Fans..
This is where Alien Covenant comes in... a movie that would cover the Xeno clues a bit... and seems will tone down the Engineer connection... but we need to remember Ridley had hinted that they still created it... and so we can expect some Engineer clues.
But i think they are now going to Milk it for a Alien Prequel to give more Alieny Monster movies and Ripley connections.
I WANDER......
If Blomkamp never showed his Alien 5 idea and concepts...
That something like the P2 movie would have happened... and that FOX would then showcase the Deacon or what happened to LV-223 in a Novelization side Story... that would give more Xeno clues and answers..
It appears now the Engineer History is to now have to take the back seat and appear in only a Novel form.