Any app store vendor is the alpha and omega on its platform. Any app store has a monopoly on its walled garden. There are some good aspects like user protection against bad apps, but on the whole, is it worth the price.
Main question now is how society should deal with this. Some ideas from the top of my head
* One option is to simply break the monopoly. A platform could be obligated to implement a store API, and the default platform store should use that same API as any other.
* Another option is a separation of duties. Just like lawmaker, judge and police can't be the same entity in a democracy, they could be split up in the app stores.
* Maybe the safety of the user device can be guaranteed independently from the app store. If the OS enforced walls between apps are strong enough that malicious apps can always be removed and no data theft is possible, the damage done by bad app stores can be lowered?