There could have been an open, cross-platform native app stack if Apple and Google and a consortium of other companies had joined forces and made it so. There's no technical reason preventing this. The economic incentives got us to where we are.
Devices should be easy to target. There should be the option to use multiple app stores right off the bat, and you shouldn't have to bundle to get access to Gmail. Or even better - point your browser at gmail.com and get the native app installed on your mobile device. Distributed updates from gmail.com sans app store. The OS would still control permissions and guard against malicious apps.
The world wide web era was truly unique and special, and it's a shame the same principles didn't carry into the mobile world.