How best can I help him learn the breadth of what he doesn't know?
I get that one shouldn't operate in a bubble, and I assume that's what you're getting at here... but does he do anything to gain exposure to outside ideas and thoughts on the tech startup scene? If so, maybe what he's doing is enough?
Has he read any books, or anything, related to this subject? If not, there's a fairly recent thread on "Good books for startups" maybe hand him a copy of one or two of the titles off one of those lists?
2. Tell him to get more involved with the startup community and in some sense, read up on things he doesn't understand. Few other cofounders sound like a bit more than necessary but since I don't know the background on this, I won't comment.
3. If he won't listen and continues doing what he wants to do, let him. He has to learn on his own. The biggest thing about any entrepreneur (the successful ones) is they must be teachable, adaptable, and constantly changing. If he is fixated in his ways, nothing you do will help.
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