I do recognise the fact that such "aggregators" would be hugely centralised (if not outright monopolised, like the search engine space). however, maybe I'm wron

I do recognise the fact that such "aggregators" would be hugely centralised (if not outright monopolised, like the search engine space). however, maybe I'm wrong but I don't see the federated model succeeding without such services either, so I think of "need for centralised content discovery" as an independent problem, honestly.