The openness issue is that Apple does not allow installs of apps outside of the app store, period. (yes, I know about ad-hoc distribution, and the enterprise program, those are very limited and still tightly controlled by Apple).
Contrast with Android, which has a market with the same advantages you list (infrastructure, payment processing, search for apps, etc.), but also allows users to install apps from other sources if they so choose, at their own risk.
Note that I'm comparing the two models, not the execution - I think Apple still has superior execution, even if I don't like the model they chose.