Thanks @csarven that's helpful. One of my concerns with JSON-LD is that it might lead devs astray in terms of the value and use of RDF.
Firstly, assuming RDF tools and libraries are more relevant to RDF and Semantic Web applications than JSON-LD tools and libraries (since JSON-LD was built for other purposes and with Semantic Web 'not even a consideration', at least to begin with). So RDF tools would I think lead devs towards uses, models and communities that RDF targets, and would I anticipate encourage practices that support the Semantic Web, and the application independence and interoperability that is fundamental to Solid. Whereas use of JSON-LD libraries and tooling could in turn discourage those desirable things.
Secondly, even if those concerns are not shared, I am at least as concerned if devs try to create JSON-LD with or without a 'dedicated library' and JSON-LD specific tooling. JSON-LD is not necessarily conformant if I understand correctly, whereas one hopes at least that any Turtle, n3 (or other conformant representations) generated by a 'dedicated library' would generate a conformant representation. I don't know if one can even be sure that JSON-LD tools and libraries will produce conformant JSON-LD, presumably not. And if JSON-LD is generated without tools it is even more likely to contain RDF bugs. So I see the need for a dedicated library as helping devs get things right, and a non JSON-LD library as preferable to a JSON-LD library at that, for improving outcomes including interoperability.
I can see why people familiar with JSON in the browser would be attracted to JSON-LD, but am concerned if that attraction might be a siren voice leading the unwary away from what might serve them better in the long term. Those are my thoughts in two large nutshells, but I admit I don't know enough to be confident of those positions, so any corrections and comments on this would be helpful. Thanks for reading!