And I'm pretty sure it was the whole point. Nobody would ever have written as many reams of marketing material if the pitch was "Hey, someday, you'll be able to reach out to the web, and with specialized software for your particular domain you can access specialized web sites with specialized tags that give you access to specialized data sets that can be fed to your specialized artificial intelligence engines!"
Because that pitch is basically a "yawn, yeah, duuuuuh", and dozens of examples could have been produced even ten years ago. The whole point was to have this interconnected web of everything linking to everything, and that's what's not possible.
Consider these passages, from "The Semantic Web," Tim Berners-Lee et al, Scientific American, May 2001:
"Like the Internet, the Semantic Web will be as decentralized as possible. Such Web-like systems generate a lot of excitement at every level, from major corporation to individual user, and provide benefits that are hard or impossible to predict in advance. Decentralization requires compromises: the Web had to throw away the ideal of total consistency of all of its interconnections, ushering in the infamous message 'Error 404: Not Found' but allowing unchecked exponential growth."
"Semantic Web researchers... accept that paradoxes and unanswerable questions are a price that must be paid to achieve versatility. We make the language for the rules as expressive as needed to allow the Web to reason as widely as desired. This philosophy is similar to that of the conventional Web: early in the Web's development, detractors pointed out that it could never be a well-organized library; without a central database and tree structure, one would never be sure of finding everything. They were right. But the expressive power of the system made vast amounts of information available, and search engines... now produce remarkably complete indices of a lot of the material out there. The challenge of the Semantic Web, therefore, is to provide a language that expresses both data and rules for reasoning about the data and that allows rules from any existing knowledge-representation system to be exported onto the Web."
I think one of the big problems with the semantic web was that it turned "varying degrees of partial progress" into "multiple competing approaches", each of which wanted to detract from the others.
That sounds interesting! Don't suppose you remember any more terms that might enable a Google search to find it?
I have a foggy recollection that Jerry Fodor (Holism) or maybe Eco had thoughts on the matter.
My core objection to "the Semantic Web" is the non-existence of "the Semantic". There is no way you can get everyone to agree upon a universal "semantic", and if you can, which you can't, you can't get people to accurately use it, and if you can, which you can't, you can't prevent people from gaming it into uselessness. But it all starts from the fact that the universal semantic doesn't even exist.
Somewhere there's a great in-depth series of blog posts from someone who describes just trying to get libraries to agree upon and correctly use an author field or set of author fields for libraries. This is a near-ideal use case, because you have trained individuals, with no motivations to insert bad data into the system for aggrandizement or ad revenue. And even just for that one field, it's a staggeringly hard problem. Expecting "the web" to do any better was always a pipe dream. Can't dredge it up, though.
(To the couple of other replies about how "it's happening, because it's happening in [medical] or [science]", well, no, that's not it. That's a smaller problem. The Semantic Web (TM) would at most use those as components, but nobody would consider that The Semantic Web (TM), at least in its original incarnation. Yes, smaller problems are easier to solve; that does not make the largest version of the problem feasible.)