During my screenwriting education, we were urged to avoid the use of narrators in our scripts. There was a good reason for this: "baby writers" tend to over-rely on narrators to provide easy exposition or bypass actual character development as they struggle with the visual-storytelling demands of screenwriting. It's challenging to learn how to describe in pictures that which you've been trained all your life to put into words. Narrators can be a storytelling crutch, so it was mostly forbidden — although a few of my fellow writers used it anyway and I don't think the consequences were too dire.
Although this trained me not use this storytelling device and I still never have, I've come to believe that not all narrators are bad. I have found the use of narration quite compelling when it's used to enhance the drama and visuals on screen rather than shortcut around them.
Here are some ways I think narration can work:
As the show progresses, the narrator becomes increasingly unreliable — and then begins to subtly hint that he is actually the director Ron Howard (which he is). Then the story adds yet another layer of irony by making Ron Howard, playing himself, a character within the show — while seemingly not being the same Ron Howard who is still the narrator. Twisting in on itself like an Escher drawing, you might lose the complex narrative threads in Arrested Development but they're great storytelling.
(Interesting side note: Barry Lyndon, a classic film called Tom Jones — also narrated in the author's voice — and Forrest Gump are all examples of a literary subgenre called the "picaresque," where a rogue or naïf of some kind experiences episodic adventures over the course of a somewhat sketchy, questionable life. Not that there are a lot of picaresque scripts floating around Hollywood these days but if you're writing one, it should apparently include a narrator!)
The main point here: in cases like these, the use of a narrator is additive to the story — the voiceover is a character all its own (often one that's not exactly matching anyone depicted on screen), and what that character has to say creates an element of storytelling that simply wouldn't be there without them.
Here is one super-famous example of when narration actually did not work:
Blade Runner. (Well, the original theatrical cut.) Studio executives demanded that a gumshoe detective-style narration be added to the original release, something that wasn't in the script, that the director didn't want, that the film's star, Harrison Ford, had to basically be forced to record. It was never planned, and so it only commented on the action; it added nothing of any significance. It wasn't a part of the story's original design.
The movie flopped. Although (because it's so good anyway) it became a cult classic, empowering director Ridley Scott to create several director's / super expanded or re-digitized / final cuts of the film, none of which use the narration, and all of which are better versions of the film. The narration didn't add anything except telegraph what the movie was supposed to be, a sci-fi gumshoe detective film (which is marketing, not storytelling). And when it was extracted, nothing was lost. In fact, one could argue, it was a better film without it … so it was actually additive to subtract the narration.