Do you have evidence for that?
then with the qualifier 'that does not restrict users and developers', what restrictions would suffice to push users and developers out vs. the incentives that drew them in in the first place.
open for openness sake is not enough - it's just one more variable in the ecosystem equation. A couple of examples: as a user I do want developers to be restricted from putting malware on my device. And as a dev I would want users restricted from going against the TOS of my app.
I think one of the advantages that Apple has over every other platform is that designers use Apple for work which builds brand loyalty to its products and platform. Thus, a good portion of the people who are creating will do so for the platform that they care about, especially one that prioritizes industrial and interactive design. And before, I would've just suggested it's just designers but over the past few years years, I've witnessed plenty of SF/NY developers who use Apple computers and iPhones for the same reasons.
The fact that it is a closed-system IS it's advantage: there is quality control across the board from the apps to the phone the user is viewing it on. And quite frankly, I prefer designing for the iPhone and iPad because of the consistency of sizing and proportions.
But there doesn't need to be a clear winner. It's great that there is a choice for people who just want complete freedom and those who just want stuff to work well in a very polished fashion.