I'm totally there with you, and my hope with DDP 1 was to make some progress on that first step: decoupling code from data, so that a standard DDP client can connect to any DDP server and pull data out of it.
In the future, I'm super excited about investigating ideas like DDP discovery (asking a DDP server what data and methods it has) and description (having a DDP server publish metadata in some standard format that explains the semantics of the other data that it's publishing in terms of microformats). I think the main place we differ is that I think that these formats should use something more like a relational model rather than a hypermedia model, or a formal knowledge representation model like RDF. Isomorphisms exist between these models, and used properly they are all equally powerful, so really this just a design decision about what will be easiest to implement and adopt. And of course I believe that it has to be server push (websockets) rather than poll (HTTP), and that it has to support server-side joins (doing 1 query rather than N+1 queries, and taking 1 roundtrip rather than 2, to retrieve your newsfeed stories plus the comments on them.) I can't tell from your comment whether you agree with that or not, but like I said, these are two of the main things that motivate DDP.
All of that said, I think that by far the hardest part of the puzzle is the product design and federation issues. In your federated Github and HN, the technical work is the first 10%, the next 90% is finding a user experience for it that makes sense to and is ergonomic for a large number of real users, and the final 90% (really should be more like 9000%) is convincing the industry (read, creating incentives to force the industry) to cooperate with the federation and to resolve all of the political squabbles about advertising, control of the data, licensing, and so on. I mean, Google pulled out of XMPP federation -- all practical evidence suggests that keeping these federation together is wicked hard.
So that's why we're just trying to build the first 10% of that first 10%, which has a very clear use case for building rich browser apps and mobile apps -- and hoping that we will be a stepstool that others such as yourself can stand on to build the full solution that everyone dreams of.
Anyway, if you are sympathetic to this line of argument, I hope you'll check out DDP and see what interesting discovery and self-description features could be built on top of it, or suggest how its semantics could be strengthened!