I just don't understand why its necessary. Prometheus could've been a direct prequel to Alien, it leads into Alien perfectly except the alien drone looks different and they changed the name of the planet. The story could've continued focusing on Shaw and David and the original events of Alien could've played out concurrently with the nostromo getting a distress signal from the engineer ship shaw and david left. Seems kinda stupid but at the same time I'm glad we're getting more of this franchise/material. I get that Ridley wanted to really tell an ancient astronaut theory movie but he didn't have to fukk up his whole cannon and do all this confusing bullshyt. Lindelof did some good things with the story but also fukked some shyt up but Ridley let him.
I think they dropped the ball with prometheus. The problem is, it didn't do either direction well. They could have gone further into the engineer mythos, seen more/heard more about our creators and all the philosophical reasons for how/why they created us and wanted to destroy us. Instead, we got 30 seconds of engineer time, he he spent it killing the group and chasing after Shaw until he got face hugged. Also, they fukked up the alien/horror/suspense angle. The aliens in prometheus stunk. The snake thing was stupid, the yoga dude was stupid, and there was no sense of suspense/fear.
This lead to audience backlash, which lead to the studio making sure the sequel distanced itsel from prometheus, hence the "alien covenant" title, and the return of the xeno, and a seemingly more typical alien movie.