That's a terrible idea. Menus shouldn't intentionally be designed to be user hostile. Instead just give a warning message, preferably one that is actually informative and appropriately scary looking.

There is a middle ground between letting any malware on the machine install whatever extensions it wants with no user consent, and banning users from installing extensions entirely.

> I really don't get how abuse of a feature is grounds to remove a feature.

If you do the right thing for your users first, this is what you do. You put user needs over developer needs.

Huh? Where does it say they're disabling developer mode? How else would one develop an extension?