I'll start off by admitting I have an engineering background so none of the material covered is new to me. The problem with any documentary is to try to keep the attention of all of your audience. You do this by making it entertaining to watch while also trying to explain your material. Hannah does a good job of making it entertaining and I find that her voice is pleasing enough that just listening is enjoyable.
Someone else pointed out that it is "fluffy", and that is a valid point. I find that all science documentaries intended for a wide audience are too fluffy, so that is not something unique to this series. Generally, I consider these documentaries successful if they can convey the basics of the knowledge without introducing any egregious simplifications. In my opinion, this series succeeds.