By July 2009, Scott was attached to direct the film, and screenwriter Jon Spaihts was hired to pen the script based on his pitched idea for a direct Alien prequel. With both director and writer in place, and pleased with Spaihts's pitch, Fox scheduled a release date for December 2011, but this was eventually dropped. In June 2010, Scott announced that the script was complete and that pre-production would begin, with a filming date set for January 2011. However, by July 2010, Lindelof had been hired to redevelop Spaihts's screenplay into a more original work. In October 2010, Lindelof submitted his refined screenplay to Fox. The studio was pleased because it had contested Scott's proposed budget of $150–160 million and found Lindelof's screenplay to be more budget-conscious; Scott had initially requested a $250 million budget and an adult oriented product, but Fox was reluctant to invest this amount of money, and wanted to ensure the film would receive a lower age-rating to broaden the potential audience.
If that's true, it shows that Lindelof was pretty much imposed on Scott and that Scott didn't have the final word in this production. Those who have the money call the shots.
Highlighted the important part.
Nevertheless, even if it was true, all it's saying was Lindelof's script was CHEAPER. Which means big CGI set pieces or whatever were cut. Characters not acting stupid... doesn't cost much.
Ridley shouldn't be taken off the hook, mate.