There are many variations of the concept that simplicity works well. Some of the more common names are K.I.S.S. (Keep It Simple, Stupid) and Ockham's Razor. While Ockham's Razor applies specifically to scientific theories, we can take a step back and examine how this affects storytelling and literature.
When designing a story it can be tempting to create one that is complex in order to create depth, or to lengthen the story. Sometimes writers, like George RR Martin, start writing and when they finish they end up with a very complex and confusing plot. The idea of Simple Done Well is forgotten by these writers and their stories are rarely successful. George RR Martin was successful due to the first three books in his series, which are well written and straightforward enough. After the third book he started to go all over the place, invent new sideplots that went nowhere, and left a lot unresolved. If only George had listened to Ockham's Razor, his story might be finished by now.
George RR Martin's biggest influence was J.R.R Tolkien, best known for The Lord of the Rings. Known as the most influential fantasy story in modern times, The Lord of the Rings created all of the fantasy tropes we know today due to its overwhelming success across the globe. Tolkien's previous book, The Hobbit, was indeed popular as well. The Nazis and English speaking Germans loved The Hobbit so much that they requested Tolkien to have it translated into German. What Tolkien did so well, and why every fantasy author tries to copy him, was create a simple story with a lot of depth. The Hobbit is as straightforward as it gets: a dragon steals a mountain with treasure, dwarves want their treasure back, they embark on a quest and slay the dragon. There's a lot more happening along the way, but the plot is so easy to follow that The Hobbit has been appropriately recommended as a children's book. The Lord of the Rings took an even simpler idea: take an evil ring to the other side of the world and destroy it. The common factor in these stories is the quest element. There's a constant goal that the readers and the characters are aware of which makes sure to maintain the focus. Tolkien's depth consists of different types of philosophy, in-depth descriptions of the environment to create a world that feels real and alive, theology, morality, character depth and small amounts of politics. Tolkien's focus on the quest allowed him to write in depth along the way as often as he wanted while keeping the story simple.
Legend of the Galactic Heroes, by comparison to The Lord of the Rings, is a complex story. It's filled with politics, philosophy, strategy, tactics, espionage and war. There's a lot that goes on, yet it's still straight forward. Its scope is very impressive and over the 110 episode run the show provides great detail about the history and political situation of the galaxy. This is where Ockham's Razor comes back in. Tolkien made a simple story, but Yoshiki Tanaka, the author of Legend of the Galactic Heroes, told his story in the simplest way possible. Ockham's Razor doesn't require pure simplicity, but the simplest possible explanation. That's how Yoshiki Tanaka got away with complexity, and why George RR Martin failed later on. Space politics is surprisingly easy to follow because there are few factions. The Lord of the Rings has even fewer factions. A Song of Ice and Fire has a ridiculous number of factions that constantly switch sides and it's difficult to keep track of everything. Simplicity doesn't directly relate to factions; it's just a common element between these stories.
Barakamon is an example of a simple show that tells a heartwarming story without any emotional manipulation, tearjerking moments or needless drama. It's about an elite, arrogant and disrespectful calligrapher who is exiled by his father to an island after assaulting an elderly calligraphy judge that badmouthed his work. The show shows the progression of the rude calligrapher into a kind, content and happy man through his relationships with the people living on the island. He becomes friends with them and acts as a mentor/father figure where he learns more about himself and about art than he ever could have by staying in the elite schools in the bustling city. Barakamon is the essence of Simple Done Well. There's nothing difficult to understand about it, but it's not forceful with its lessons.
However, all the talk of simplicity working cannot discount when a complex show is done well. The distinction between complexity done well and simple done well is a lot less clear and far harder to come to a conclusion on. Serial Experiments Lain, for example, is a very complex show and it's thought provoking, internally consistent, accurate with its predictions and incredibly well produced. But whether simple is done well or not, it will always be better than complexity done poorly. A convoluted mess of a bad story is far worse than a clear and obvious bad story because you can at least understand the simple one. Simplicity is far easier to do than complexity as well, meaning that aspiring writers should focus on making something simple and improving upon it rather than jumping off the deep end. There are few authors who have successfully made a complex story and fewer still that have made one commercially successful.
I am always open for a discussion, so if you have any examples of shows that are Simple Done Well, or are relevant to the concept, please post a comment and we can talk about them.