I'm sure that a Chinese author discussing the impact of the cultural revolution is going to pose harder moral issues than Tolkien did in general, and its quite correct that Tolkien's best known works (TLOTR, Hobbit) have fairly simple morals.
Ultimately authors have chosen for whatever reason to tell the story they want to the way they want to. George RR Martin famously likes to get on Tolkien's case for not answering the question of what exactly does it mean for Aragon's rule to be peaceful. I don't think that that criticism is entirely fair. In LOTR, Tolkien had a specific story he wanted to tell. He did it to amazing effect, with thorough character development and world depth. You could not look at his work and say that any of his characters did not behave logically to what was established within themselves. Particularly with the Hobbit I think you can tell that he chose to tell a specific story and to do that erred towards moral simplicity. But that doesn't make the story any less beautiful -- in fact, I would argue that the innocence and purity of the hobbits against this unknowable and extreme evil is part of LOTR/Hobbit's charm. It allows him to tell a story that is fundamentally different from the story JY or GRRM wants to tell -- which is how your innate goodness, if you continue to tap into it and grow it, can help you triumph over corruption and evil. Frankly, I find that this kind of story is something that we are quick to want to discredit because we think it lacks "depth" and is too much of a fairy tale. So, that he can tell this kind of story so effectively and meaningfully is something to be cherished.
> But that doesn't make the story any less beautiful -- in fact, I would argue that the innocence and purity of the hobbits against this unknowable and extreme evil is part of LOTR/Hobbit's charm .... Frankly, I find that this kind of story is something that we are quick to want to discredit because we think it lacks "depth" and is too much of a fairy tale
Yes, completely agree. Tolkien's formative experience (analogous to the Cultural revolution for JY??) was the First World War, the death in combat of most of his closest friends and the characters of the ordinary soldiers he met in the trenches. He explicitly made the connection between these people and characters such as Sam.
Some of Tolkien's characters find themselves in some morally complex situations. For example, Niënor who finds herself pregnant after an incestuous relationship with her own brother Turambar, due to a spell of forgetfulness cast by the dragon Glaurung. It's not all hobbits worrying about second breakfast :-)