Intelligence is really nothing more than another form of comparison. Grades and IQ don't mean ****.
"Yes I'm smart compared to my class mates."
"No, most people know more than me."
"Yes, I get good grades."
"Yes, my grades aren't good, but I'm socially intelligent."
"I know a lot about the world, although I'm not book smart."
Anyone can be intelligent if they just have the interest, motivation or the qualities that everyone else sees and thinks "wow that person is intelligent". Everyone has the capability to expand their knowledge; they either don't care enough or are convinced by themselves or others that they're incapable of learning.
Besides all that, it's not a thing to be ashamed of if you're unintelligent/not book smart. I'd rather hear the words, advice and stories of a welder on an old forgotten highway than a 22 year old university graduate.