As the saying goes "In the country of the blind the one-eyed man is king." I am sure all of us are experts in something or other relative to the world in general. But are you willing to stick a metaphorical shell outside you door and say "I am am expert on X. Consult me to learn something"? As I suggested, there's not a lot I feel that confident of, personally.

But I accept that is perhaps an artificially high level and maybe most questioners would be a someone who knows just enough to get them past their current hurdle.