Or they accept the push notification dialog on some random site and start getting "COMPUTER HACKED, CALL MICROSOFT AT FAKE NUMBER" notifications that look like they come from the OS.
And then, billions of users cry out in pain as their private data is hoovered into the panopticon in the cloud.
That's not how data collection works? It's Apple's responsibility to prevent their application runtime from exposing private data or unnecessary entitlements. Enabling sideloading does not prevent Apple from protecting user data any more than the App Store does.
Then it would be legal for someone to develop and give-away a patch for the Meta app...
Yes, in an ideal world, that might work but most people don't actually know they have malware. That's the point of the malware! And it's not like you can say "no internet for you until you replace your TV[0]" because that's an extremely quick way to the courts and a customer reputation below the toilet.
(Ignoring the "who pays for that?" question because that is a whole 'nother can of worms.)
[0] https://www.ibtimes.co.uk/fbi-google-disrupt-proxy-network-a...
It would be foolproof, maybe the most trustworthy system ever conceived.