The problem here is that the system is not secure by default, one needs to hire a qualified specialist to set everything up. By default the user can run executable attachments or files downloaded from browser and it is a wrong design decision made many years ago. Users do not understand what is an "executable file", they got used to click an icon to see the file contents. This is just poorly designed UI that helps to deceive a user.

> If Microsoft forced either SmartScreen OR AppLocker, then we'd have people on here screaming about freedom, Microsoft is evil,

There could be a separate UI for installing software or even a package manager. Microsoft doens't want to change anything because it is still the leader and earns huge profits.