I'm adding JSON-LD / schema.org to a couple apps with a million pages (legal publishing).
I've had Dublin Core embedded in the pages for years, but don't know of any benefits I've received from having these 12 or so
meta tags. There's definitely a maintenance cost (and secondarily byte count). Just looking at the tags, I can see I need to put in more time to verify I'm using them correctly, etc.
I've never heard or detected any benefit from having them: SEO, inter-connectivity, or otherwise. On the other hand, I've seen the direct benefits of using JSON-LD / schema.org in my pages: better semantic search result presentations, and custom tailored metadata about my content.
It seems that Dublin Core is superfluous and costly without benefits in my situation. (?)