In another comment[1] I describe software I've made that solves some of these challenges.
A searchable collection of data is great if you have a use case that actually depends on such a collection, like writing a paper, news article or doing (academic) research on some topic.
Maybe to ask a better question, what data do you want to collect and what are you using the data for exactly?
If there were a clean distinction between entities and tags, existing solutions would be enough. But what if you want to draw a relationship between two relationships? Most sentences longer than three words, after all, are higher-order relationships. ("Birds #avoid beetles ##because beetles #are hard to digest", for instance, is a second-order because relationship joining two first-order relationships.)
The searches Mr. Borichevskiy imagined are, I think, good arguments for why you would want to be able to encode arbitrary higher-order information. I believe Hode is the simplest solution possible that allows it.
Personally, I'm kind of glad to soak up information as I go and being able to just forget everything else. As opposed to constantly feeling the need to tag, sort, archive, reference, cross-reference, keep track of information, that future self will to 99.9% never actually need.
Yet, I wonder whether use cases start to materialize, once you start using it...
Federation could reduce the hurdle -- both reducing the need to ingest, and the difficulty of doing so. Borichevskiy (author of article that generated this thread) nods at the idea of using someone else's index of books. Such labor-sharing could be much more general.
I don't want to suggest, though, that ingesting something is a waste of time if you don't review it. That's true of boilerplate metadata like ISBN numbers. But for original ideas, or for paraphrased insights gleaned from reading online, I find that sticking it into the graph produces value at the moment it's done. The rigor of compressing an idea to a few words, and determining which adjacent concepts it bears on, and how, has helped me understand things.
(Teachers often ask their students to state things in their own words. It's like that, but faster and harder. Like punk rock for essays.)