Seems to miss the obvious double whammy: 1) Because it burdens producers to no obvious benefit, a problem forever 2) Because progress over time in language processing makes it less and less necessary
A refinement on your second point is that the groups who would have benefited the most from semantic web were the googles of the world, but they were also the ones who needed it the least. Because they were well ahead of everybody else at building the NLP to extract structure from the existing www. In fact the existence of semantic web would have eroded their key advantage. So the ones in a position to encourage this and make it happen didn’t want it at all. So it was always DOA.