Hahahahaha they also come in Debian .deb and Fedora .rpm packages. That’s why I never got this problem with my hardware on Ubuntu or Debian.
That is exactly why the AUR exists. To repackage that vendor's .deb into something Arch can safely manage. This makes Arch support to 3rd party apps almost unbeatable.
And you’re right: PPAs are not the same… in this regard they’re actually worse. AUR is at least in plain text and the documentation is clear: always check the PKGBUILD. When you add PPAs you’re blindly trusting a 3rd party repository and updating them with sudo.
You can’t burn the whole thing down just because, in your own words, “people are stupid”. They either read the documentation and follow the security policies, or they stick with Arch and Flathub. Or, they can simply choose a different distro. It’s that simple.
The thing is, I agree that AUR could have some sort of protection, such as a rate-limiting or a reputation system. But even as is, AUR is still an excellent feature that should definitely be maintained. And people, specially using Linux, definitely should educate themselves instead of exclusively rely on strangers for all their digital security.
Edited for extra clarification.