Indeed, thinking that your system is safe in any default configuration (unless you use OpenBSD, even then you shouldn't overlook security) is a bad idea. Users these days expect stuff to "Just Work" , and that requires vendors relaxing security features so users don't complain about things like "Why do I need an administrator account to install this program?". I'm unfortunate, but that's how things are.
Personally, I still love a Mac

It's got Unix-based underpinnings with a sexy interface. You can't get much better than that...