and oddly, even though I'm probably the best at going on and on about things that I find interesting, no one seems to want to want to hire me. I don't think this is the full picture.
I don't know if this is what you're referring to by the phrase 'going on and on' but the phrase makes me think of my coworker who talks in circles about any topic, providing many words but little info. And the circles usually incorporate personal anecdotes. He hasn't realized people tune out immediately.
I don't care so much what you find interesting per se. I care about the intersection between what you find interesting and what my company does. I care how good you are at doing that kind of work, about your confidence that you can produce and solve problems without me needing to hold your hand all the time, and your likeability. If you can demonstrate those things better than the next guy, you'll probably get the job.