I read on a webpage that neither bad, nor good scripts ever get made. They said that you must have a ”killer script”, unlike 99% others. Could you please explain what does it mean? Thanks for answering!

A killer script is one that you read and seven days later a lawyer from the MPAA crawls out of Hell and gives you a subpoena to a court trial that says you violated copyright laws and will be punished with a lethal injection.