What took its place in your experience?
In the Bib world things like the Virtual International Authority File (VIAF) so every system talking about the author Charles Dickens used the exact same identifier for him, allowing different data stores to be easily traversed and linked together, by design.
I write “mostly” because recently neo4j has a “neosemantics” project which handles RDF. It is all pretty standards compliant RDF though, nothing custom at all.
For more information this may be a good start: https://neo4j.com/blog/rdf-triple-store-vs-labeled-property-...