> It also reminded me what an excellent job Wikipedia does with their hierarchical classification

As someone who once tried to use that supposedly hierarchical classification for data organization, it is unfortunately not excellent at all.

It is rather arbitrary, inconsistent, extremely incomplete, and not infrequently circular. Think of it more like a bunch of haphazardly applied tags that make perfect sense in the context of a single page, but quite frequently make very little sense when you look at the actual pages and sub categories that belong to a category. Category membership is just not something visible enough for it to wind up being organized and curated in any kind of systematically accurate way.

On the other hand, the presence of an infobox of a certain type is extremely reliable for categorizing many types of articles.