I took a brief look at this map as Sonnyc showed me, and the main problem with the Beginner diff I think is that it has too little rhythm variety to show the song's changes. The 1/3rd beats are indeed most important beats, but that doesn't mean these beats show any kind of properties that this specific music has. Literally 90% of other songs out there can also be represented only with 1/3rd beats, or even with the 1st beats only, if you only prioritize the most important ones with such a low intensity, but that doesn't mean the map represents how the song really sounds like. There are rhythm patterns that this specific music only has, and I think you could try to represent them more while keeping this intensity. If not, then maybe this diff is just too easy to represent this music at least to a certain point.