Well, the app might be currently available in the AppStore but would now be able to move to an AltStore. Plenty of apps I bought in the past have been pulled from macOS AppStore but are available on websites.

In the past I even had banks and even the public sector offices abusing Windows and macOS security and forcing me to install the equivalent of a rootkit in my computer. Without a sufficiently smart sandbox I bet this problem will come back.

On the other hand, that doesn't seem to have happened on Android, at least not in a wide scale.