Screen tinting like that is exactly the kind of thing that should be an OS-feature, not an app feature.
They are similarly quite restrictive on MacOS, with some system-impacting features being locked behind “accessibility” permissions. So that arbitrary apps can’t interact with other apps unless they are actually doing something that needs it like “being a screen reader”.
iOS doesn’t have the same sort of permissions. Apps can’t take over interactions with other apps, or change display settings, etc. This is a security boundary. And changing that specifically for “changing screen colors” seems unnecessary to me.