It's a little unfair to the first Alien movie. It's been a while, but the first one is often hailed as an example of everyone acting as intelligently as makes sense for the character's job and motivation.
Prometheus in the other hand... I think Ridley Scott doesn't respect scientists very much.
Scott obviously hates scientists or is completely oblivious to how science works. The crew is the least scientific group of people ever assembled on film.
The Prometheus cost a trillion dollars and Wayland is betting his life on the success of the mission, but off the top of my head:
The scientists aren't told what their mission is until they arrive at their destination which is so ridiculous, but you can argue that's what they signed up for, so okay. But that gives no one a chance to say "oh, then we should pack this odd piece of equipment."
Wayland's presence isn't known to the crew, so no one is prepared as any sort of backup to David other than his daughter.
There's one autodoc and it's only configured for males so again... Travel to another star after spending a trillion dollars with no backup? But somehow it can perform a C-section on a female with an alien in her. Okay.
The pilot has to stand up? Really?
The atmosphere is breathable so on that alone they take their helmets off. Sigh.
He should have brought the scientists and engineers that designed, tested and built the ship itself, because they were good.
I mean the list is just goes on and on about how unscientific the mission is. There's a whole cottage industry of youtubers pointing out the innumerable flaws in that movie.
Of all the bad ideas to happen in that movie, including the "let's not let the audience know what the robot said to the alien", that has to be the most baffling. All it did was break immersion. Why couldn't the ship have fallen over and slid down the mountain? It's would have been as terrifying as an avalanche in a survival movie.
FYI if you really want to know there's a guy on YouTube (Kroft) that has done dozens of very good videos on the Alien movies. He breaks down what was said as it was in the original script. And it's interesting and would have made a better movie, but I think Scott chickened out of the potential controversy.
Long and short of it is that >!2000 years ago the Engineers had taken a human to their home world and trained him and enlightened him and sent him back to earth to spread the message but his compatriots nailed him to a cross.!<
!The Engineers, therefore, decided that our race was a failed experiment and decided to exterminate us but their own weapons got away from them and killed them before they could pull it off.!<
There's more to it, but go watch Kroft's videos if you want to know more.