It doesn't need to emulate to be just as big or bigger. What do the big platforms all have in common? The fact they're all different. Why should Hive emulate reddit when a variety of multi media sources on chain would appeal to far more people.
PeakD comes the closest to this central hub style app. It gives you somewhat easy access to many other products on chain. Those products don't send you back to a home base though. It's not all tied together, just linked together halfway and haphazardly. Someone could stumble into a Tribe site for instance, and not know about other Tribes or even Hive in general without browsing the site for a long period of time and stumbling into random content mentioning those things, but only if the timing is right.