I am also frustrated with Wikidata. The one practical use I've seen is a lot of OpenStreetMap places' multilingual names are locked to Wikidata, which makes it harder for a troll to drop in and rename something, and may encourage maintaining and reusing the data.
But I tried to do some Wikidata queries for stuff like: what are all the neighborhoods and districts of Hong Kong, all the counties in Taiwan, and it's piecemeal coverage, tags different from one entity to another, not everything in a group is linked to OSM. It's not a lot of improvement over Wikipedia's Category pages.
Frankly, I think the reason people haven’t built apps on top of Wikidata is that the data there isn’t very useful.
I say this not to diss Wikimedia, as the Wikipedia project itself is great and an amazing tool and resource. But Wikidata is simply not there.