Sorry, but I respectfully disagree and think you may be the one misunderstanding what choice is here. Having only one option for your apps and payment methods isn’t a choice. If Apple did open up, you would have the choice to not support apps that make you download something outside of the App Store. That’s your choice to make, and voting with your wallet. On the Mac, you have the choice to purchase from the Mac App Store, or directly from a developers website if they make their app available in both. That’s a choice.
Opening up the method to get apps on an iPhone doesn’t turn iOS into Android. You still have the exclusive Apple features like iMessage, Apple Pay, Apple Wallet, Siri, iCloud Photos, integration with other Apple devices, better security, privacy, sandboxing, etc. These features and more are what make people stick with Apple, not the lack of choice in app stores and in app payment mechanisms.
I understand many people on here love Apple, and for good reason. They make great products and are the hardware leader. But that doesn’t mean that their way is the correct way at all times, and I do believe that the lack of App Store choice and in-app payment methods will have to change in the future. I also don’t believe it will lead to a massive influx of malware. If the code of iOS is as secure as Apple claims, and apps have to ask for permission to access your camera, mic, location services, contacts, etc, you will know if an app is accessing something it shouldn’t. If iOS is only secure because of a locked down App Store, we probably have a bigger issue to worry about.