To me, subtelty and thus Not treating the audience as idiots, is a big factor when it comes to good and mature writing.

But I'd argue if the piece is lacking the first place whether it be the story, production, characters, why would you care to look to look at anything subtle it may have? It does show that there was some passion thown into it, but the first job of a piece is to captivate the audience, how that goes is up to the piece whether take a straight forward or artistic route. Princess Tutu for example from me is something that is subtle with poetic themes, and it has the story the characters along with its animation and imagery to carry that further where I'm fully with it and later willing to take myself out of the piece not because I'm bothered by it but because I want to know more of what the subtle themes are trying to express and how it inserts it through different means. But if we look at the opposite spectrum, Plastic Memories in this case has some subtle base to cover with it, but it lacks highly in character where they're bland cardboard cut outs, I'm more distracted by them and bored with them that I don't care for anything the it tries to do being subtle.

It's the first job of the director to immerse the viewer in his world that he sees the characters, and sometimes that begins with the very basics. They can try to subtle all they want, but if the viewer is bothered by the piece in some way or it doesn't interest them, then the subtlety just goes to waste and doesn't really make up for the flaws. Art (IMO) is how we can emotionally connect with those in the process of creating it, it's illogical, and I mean that is if trying to judge from a logical (or objective) point of view it would make no sense and there's no point to art, one must let themselves be in the piece and it's when their taken out of it that it becomes a problem.