How is this different to the status quo of hundreds of millions running old exploitable versions of $BROWSER, infected with malware which hijacks your internet connection? All you've done is swap one delivery mechanism for another.

You don't fix this by switching out automatic updates for manual ones, because users will blindly install an update even if it's a badly-designed 'update dialog' popup on a shady website. You fix it by ensuring users can trust their software, and care enough to do so.