"It basically implies that you can ignore people who have blogs and podcasts. Seek out the unknown experts in your field."

Fully agree with this. But it seems not easy to find hidden gems. It takes time and energy to deliver what's in one's mind. Take this into account, what we can find is only a fraction of the real gems with lots of noises mixed with them. The best shot I can think of is to have some kind of small circle to exchange ideas and opinions. Another resource is reading books, I guess.

As for famous people's wisdom, they have way more access to information average people don't have. And the average quality is probably better. Just like what the artists do you mentioned, they do the same with information.