Android phones come in all different sizes and they don't have big black bars. Apple controls both the hardware and software, it is inexcusable.
Apple doesn’t control if an app developer updates their app to support new screen sizes.
Also, in the case of the screen shot with Pokémon Go. The iPhone X is not yet released and therefore the update to Pokemon Go to support the X’s screen ratio cannot go live onto the App Store. It’s the same when for example apps updating for iOS 11 could not go live on the App Store until iOS 11 went live.