I'm not against notarization as long as it's free (akin to Let's Encrypt) and strictly used for combating outright malicious software like you described, and not as a way to keep competitors off the platform, rent seek, or ban apps for "philosophical" reasons (like NSFW content).

They're intentionally conflating these objectives to give themselves an excuse for maintaining their stranglehold on users and developers alike. They need to give up some ground if their security concerns are to be taken seriously.

I'm sure all the smart people in Cupertino (and elsewhere) can figure out some really great solutions for protecting users in an honest manner, if only their leadership didn't instruct them otherwise.