If you're willing to work with the JVM (i.e. through JNI), there's really nothing stopping you.
You can 100% make entire apps using nothing but C, C++, or whatever, as long as you're willing to interface with the JVM that's created for you to access Android APIs.
But the Android API is a JVM API. There's no getting around that. At this point, it's another OS (i.e. not Android) if it doesn't have Java in it.
Comments
If you're willing to work with the JVM (i.e. through JNI), there's really nothing stopping you.
You can 100% make entire apps using nothing but C, C++, or whatever, as long as you're willing to interface with the JVM that's created for you to access Android APIs.
But the Android API is a JVM API. There's no getting around that. At this point, it's another OS (i.e. not Android) if it doesn't have Java in it.
Actually there was such OS, Android Brillo and the OEM market said no, hence why it got replaced with Android Things, which re-introduced Java again.