[T]he old-school rules of objective journalism exist for a reason. They protect reporters, subjects and stories from being influenced by emotions. Breaking those rules is fine, as long as expectations are set correctly. The fact that people are upset at Serial’s ending indicates they weren’t.
On the contrary, I think Sarah Koenig did a great job emphasizing that it’s not a fictional drama series, but a real-life event. Adnan Syed is still in prison, and it’s continuously referenced throughout her reporting on the story. If people are upset, that’s an indication that Koenig did a great job of making such a contrived decade-old case so compelling.