One other issue is that even at a startup that did this right, you're still in danger of learning from a smaller set of individuals. It can lend itself to group

One other issue is that even at a startup that did this right, you're still in danger of learning from a smaller set of individuals. It can lend itself to group-think / inbreeding. I'm not sure that startup vs. big company is useful anymore, if it ever has been. You can be in a team in a big company that is an awful place for learning, for example.