https://github.com/orgs/stardog-union/
Looks like Knowledge Graph and semantic reasoner are the search terms du'jour, I haven't tracked these things since OpenCyc stopped being active.
Humans may not be able to effectively trudge through the creation of trillions of little rules and facts needed for an explicit and coherent expert world model, but LLMs definitely can be used for this.
Of course the underlying storage can be (and often is) a bunch of specially prepared relational tables.
But the strength in graph databases comes from restating the problem in different way, with query languages targeting the specific problem space.
Similarly there are tasks where SQL will be plainly better.