Hoi,
As far as I am concerned, the categories used for images are not really helpful , While there are many images about Kiribati, you find only a few in the category by that name. The rest can be found in subcategories.
In the proposal for Commons there is a provision for tags. These tags can be populated to some extend by the categories they are in.
The reason to have categories is because they are intended to help find images. Without them and without tags we would not have Commons as a functioning entity. However, the way they work with all these subcategories and stuff prevent many people including myself to use Commons as the source of images when I need them.
So yes, having categories are good in a half arsed way but we should get rid of them as we can have something better.
One other big advantage of tags is that they are typically single concepts that have typically have translations either in the labels in Wikidata or in Wiktionary. This allows us to make Commons a truly multi-lingual resource.
Thanks,
GerardM