What if things had to be a certain way? Characters are not being portrayed badly, but the characters themselves are all portraying themselves falsely...
David is secretly the most real... his twitchy nature makes him more human than the humans of the story. He secretly displays more emotion than the subdued emotion/acting and fake personalities of the crew.
What if even if the actors could have improved their performance, Ridley made everyone minus Shaw and David tone down, or alter their normal acting style slightly... forcing the characters to use cliches that are all incredibly old by that point in the timeline... a culture that may have gone stale like the Engineers. Because Weyland gave them everything and rules like a king. They're all his subjects. Tools.
In some basic ways it's a lot like American Beauty where David=Lester. In American Beauty it's made out to make Lester appear as a somewhat bad guy responsible for all his own problems when you first watch it. If you dig deeper into the movie you realize Lester is trapped in a situation and it's the only reason he acts out irresponsibly. As a way to escape the miserable life he's trapped in. As much as Lester can't take control of his situation completely, or change it; it's the others around him who are also at fault and secretly more crazy than Lester appears to be. The wife drove him to his misery/actions. At the end his death is a misunderstanding caused by the father of the boy next door who he was only smoking pot with, and the father of the boy has serious issues. All the characters in the story except Lester have been adding to his inability to escape the situation and his breakdown. Here it would be all of the characters except Shaw and Janek who are secretly less real and more crazy than David...
We have to remember this is Ridley's vision of the future, plus the quotes Lindelof said about getting inside David's head and the "robot's perspective."
David subtly indicates he may want to kill his parents. There may be a reason for that.
He hates his parent-- the unjust king who forces him to do his evil bidding... as well as the culture he's been born into.
These are not colony born humans living out in space.
They've been directly under Weyland's rule as king for a very long time.
These characters were born into the culture Weyland helped shape and morph-- giving them all the answers, making them dependent on him as a leader. Portraying himself as a god.
It's a nature/nurture thing after David's birth. The characters are the way they are because they've lost their true selves, true emotions, and are less real than David/Fassbender.
Ironically David is becoming a "real boy" and Shaw and Janek are the only others who come close to being "real". With Vickers she pretends to be in control and emotionless, but hides her own unbalanced emotions, panic, fear, and risk aversion based emotions for the most part.
And there's something very different about most of the Earth-born humans of this time minus the above characters.
It's like people like Ford and Jackson are a little bit emotionless and a little bit too unthinking/obedient and unquestioning.
Holloway connects with his emotions too much, unlike the rest, but has major ego and false ego problems as well.
The characters' "fakeness" could be a reflection of Weyland's chaotic rule over the timeline. More so than that each character may be hiding their own full views and perspectives, agendas, and true nature. So the emotions they display on the surface are fake... David is actually becoming emotional... more human than the humans he's with.
The humans of the story can't even take care of themselves or respond logically and instinctively at the same time to either run away or fight the situation. This is displayed partially by Millburn's inability to control the situation(though he pretends he can) or even to simply run away (flight response). They've lost some of their survival instincts...
On one level David is absolutely telling the truth when he says to Shaw: "I didn't think you had it in you, poor choice of words"... because there are multiple meanings to this statement. Meaning on one hand that her survival instincts are impressive compared to the rest, although he could still be being sarcastic and is disappointed he was wrong about all humans, "not too close I hope". Her true logic and intuition/emotion combined in a way that leads her out of the situation. Her "realness"... She's different from the other humans he's grown to despise. There's a reason he says "parents (plural)" and only has the one closest thing to a father... again it's a nature/nurture thing and he sees his other parent as all of humanity. Possibly just the company, because he may have a pseudo-subconscious desire to replace his parent and become King... he feels superior to Weyland and humanity... A lot of Weyland rubbed of on him. More than the preference for Lawrence of Arabia...
He may actually be admiring Shaw's ability to go against Weyland's programming, but at the same time it's a poor choice of words because he's revealing he can lie. He had full knowledge that "it" was inside her in his other meaning.
He may also have a little respect for Shaw because she taught him to choose what to believe when he was watching her dream, which is how he lies and deceives-- choosing to remain vague throughout the entire movie.
The characters are all too egotistical, greedy, unable to see other perspectives, unable to connect with their emotions and intuition properly, semi-uncaring, fake, semi-unquestioning, and semi-emotionless because of Weyland's influence over the culture they were born into. A lot of it rubbed off on them because he's the parent of Vickers and David, and like the King of the culture for the rest. Even David may become like his father, like the father he hates, wanting to be a creator as our first near-immortal character of the story. "Sometimes to create one must first destroy". He's an android head that gets to keep living without anyone having to plug anything in or trick it into thinking it's alive again. David's head is immortal in a way that the later Androids aren't. The old order at Weyland corp is completely destroyed and begins to disintegrate when the King is killed and the Weyland lineage is severed.
There's something going on in David's head. Look at the early posters that focus on David, and the links between all the head themes become more apparent. The focus on David in general and how Fassbender came across as one of the best things in the movie should provide some clues that a lot of the series will be about David.
In the beginning we see Millburn using a different accent when conversing with Fifield for the first time. He later switches to trying to impress him when Fifield turns out to be not so tough. Millburn tries to impress Fifield and foolishly believes in his abilities/act enough to try to pretend he has the situation in control. He almost accesses his flight response when he almost backs away, but his false ego takes over and he goes forward thinking/believing what he says.. That it's mesmerized and he can handle it. But he really has no clue what he's doing.
Janek is the natural captain and leader but he purposely gives up control of situations sometime prior to the events of the movie, he "just flies the ship" but at the end Ravel or Chance (can't remember) reveals that he's a "shit pilot". It takes a long time for Janek to take charge of the situation but he makes the call Vickers couldn't make and Ravel and Chance stick by him. They believe he's right-- they're both betting on him...
And of course after the deleted scenes and all we know Janek may be almost entirely right with his view of it being a weapons facility, because of his past experiences and having been in situations where tough calls had to be made.
They're supposed to be acting like irrational, illogical morons at times who can't properly combine logic and intuition/instinct/emotion anymore to begin looking for evidence in the right directions. Because of Weyland's influence over the culture. As a king, as almost a dictator.
David is breaking free from what most humans from Earth are like at this point and in the future of the series. "Earth, what a shit-hole"
