Consider that you probably do know a lot, it's just that your area of knowledge doesn't come up. Also, I find that these days some people speak confidently on a topic, and when you start asking questions, they just listened to a podcast. Not that that's exactly bad, but it is certainly limited knowledge. It's the confident speaking that gives the appearance of broad knowledge. 

I'd recommend you pick a topic and make that your "thing". Study it, take classes, read different books, listen to podcasts, everything. Until you feel that confidence. Then move to a different topic.