Hierarchical taxonomies always run into problems because there are multiple equally valid ways to organize things. Hierarchies are inherently a wrong-headed approach. Subjects are inherently multidimensional. Hierarchies wind up forcing you to stack categorization on different properties on different levels of the hierarchy and it winds up arbitrary which ones you preference over others.

The tendency to reach for hierarchies is a bias we inherit from life in the physical world. A physical object can only be in one place at a time, so we organise physical objects in hierarchies by necessity. Rooms, cabinets, drawers, files. This is not a necessary limitation on computer system but people keep insisting of using them anyway.

Have you ever used bank software, or some government services site? It is often really hard to not get the idea that it was designed and run by idiots. As someone who’s worked as a software developer most of my life, it is not difficult for me to believe it, either.