It's this very awareness of one's own limitations that allows folks to overcome those limitations. If I might add my own (personal, biased, narrow) understanding; the whole concept of "stupid" is like a cognitive filtration mechanism. We filter ideas that others have by calling them "stupid" and then we attempt to avoid being filtered in that way, but that filter is kind of stupid. Unless you already know everything (protip: you don't) you run the risk of filtering based on an incorrect assumption.
No, I often legitimately think that my question might (!) be stupid, because I'm aware that I'm coming into the discussion with less domain knowledge and experience than the other people in the room. I still think it's good for everyone (ie, not just me) to explain. (Sometimes it's clear that everything is just out of my league, in which case I shut up and let the meeting go on.)