The first red flag I see is that the app isn't multiplatform. I know there's plenty of iPhone/Android exclusive apps, but I will very rarely use (much less spend money on) something that is locked-in to one app. Also, does anyone else find it ironic that a habit tracking app has a monthly subscription? Feels darkly ironic looking at the IAP block towards the bottom.
This doesn't matter to most users (of a given target platform), and if you're charging money for an app—rather than making money with ads, or providing a service that needs maximum reach or user base, or relying on network effects to somehow make money as e.g. a messenger or social network might—then you only need/want iOS until you are seeing enough traction to be confident that the lower sales rate on Android will nonetheless be high enough to make it worth it.