It is a big mistake to say that RDF/semantic web has "failed".
What has happened is that people have tried a lot of things and some have succeeded and some have failed. For instance, OWL seems to have become an inpediment to progress rather than a useful tool. On the other hand, people are starting to understand what JSON-LD is and they like it.
Also note that by simply specifying a namespace to put the terms in you can transform JSON into usable RDF and even put multiple documents in and see them as a comprehensive graph.
What has happened is that people have tried a lot of things and some have succeeded and some have failed. For instance, OWL seems to have become an inpediment to progress rather than a useful tool. On the other hand, people are starting to understand what JSON-LD is and they like it.
See https://developers.google.com/schemas/formats/json-ld
Also note that by simply specifying a namespace to put the terms in you can transform JSON into usable RDF and even put multiple documents in and see them as a comprehensive graph.