Its a massively disruptive company that is only relevant for few to actually interact with. Their problem is that their market is quite small, but their importance is so high.
What is Twitter? A news / information filter bubble generator which rapidly bubbles discrete information into relevance quite quickly using the network effect as well as social bonds. This is essentially what Google news and anything on Facebook is desperately trying to do algorithmically by scanning through how people interact with the incoming information. I'd personally say they are failing badly in producing relevant content in themselves.
Twitter gets it for free. Why can't most people 'get' twitter? One, as described above, its a information dissemination engine. Most people can't know or even care about being a part of the information, so they're almost entirely consumers. The consumers of twitter then take relevant information already rung through the twitter world to refine them into a narrative for their already captive audience. The audience doesn't care which hashtag that's trending or why (largely), but rather information relating to their already established interests, like stories that make political candidate X look like an idiot, or a crook, or paid shill, etc.. So the tip of the filter bubble are those sites / tv / etc.. extracting from the engine to disseminate further.
So why don't these taste makers / king makers use other platforms? I suppose its largely about being established as 'the' place to disseminate information. It helps immensely that Twitter doesn't fuck around with curation and 'hot' lists nearly as much as the others. For better or worse, when people talk about Twitter, its 'a platform' aka infrastructure (a very valuable one), whereas the other services are 'services' to consume at least from a broad audience perspective.
There's no confusion in Twitter in terms of what they're good at. They know what their platform is good for. They just can't find a way to sell the platform to the outside world, because they have no interest in being involved in the narrative (which is probably for the best anyway).