Allow me to explain what is implied: More options for ways to get apps won't make app developers more money. This is shown by the difference between profits developers get by developing apps for iOS vs Android. Android has a larger user base, but it's still more profitable to develop for iOS. That's how it affects devs.
Less money to be made means devs are less incentivized to put as much quality into their apps. Some still will, of course, but others won't, and some will simply stop developing for the platform, so average app quality goes down. And less restrictions mean more crappy apps out there. This is how it affects users.
I'm not saying either system is better. I fully sympathize with the hurt of the 30% cut that Apple takes. And I sympathize also with wanting a more open platform. All that I'm pointing out is that by opening up Apple's platform in the way you're proposing, it will indeed affect everyone in some negative ways. There will be positive ways, too, of course. Such is the nature of change.
