Package managers do not magically solve the problem of malicious programs, just as their big brothers, app stores, don't.
Of course you fully ignored the main point, which is that Linux protection features are completely out of sync with the needs of a modern single user desktop, being ballast instead of a benefit.
In response you seem to enter panic mode. Your last line even denies me reasoning, as if I can't have an argument unless an alternative exists.
So I guess you are exactly sensitive in the way I explained, presumptuously assuming Linux/Unix is the only true OS, employing the best minds, the winner. And more wishful and dangerous thinking like that.
The fact is Linux doesn't care about the user unless he is the sysadmin. Linux is the sysadmin wet dream. But you know what? People hate the sysadmin, and don't want to be one. They do not buy the gospel, and ultimately that is because Linux is an ideal not of this time and age. Linux is a castle, not a house, not a place to live in.
It's not that they are sensitive. It's that you are so completely, ludicrously wrong that the overconfident tone is borderline offensive.
> Why adopt something that is on its way to the museum?
For it to be headed to the museum, there would need to be something better. Can you point us to it?
> users badly need protection from downloaded programs which can't be fully trusted.
Linux solved that issue decades ago. It's called a package manager and you should read about them.
> There are no other users on the desktop
Think on how browser exploits work. Come back when you understand it.
> On the desktop Linux is simply unfit.
So, what do you think is a better fit? Macs?