> simple viruses
Read these words again. Regardless of whether there were tons of viruses on MacOS back in 1997, there's no way it's valid to hold up your thumb, squint, and say the current situation is better or worse. The malware on MacOS 8 was almost exclusively viruses made by hobbyists which self-propagated through channels that no longer exist. There were no command and control servers, strong encryption, muti-stage deployments over the web, etc. Modern malware is organized crime that relies primarily on people scamming other people, and requires a ton of back-end infrastructure and support.
In other words, it's harder and success depends on a whole different set of factors.
The person I was replying to was basically asserting that Apple fixed the virus problem that existed before OSX, and as a result malware cartels in 2017 aren't able to attack OSX. Would you believe it if they were saying polio vaccination campaigns in the 50's put a dent in drive-by shootings in the 90's?
That doesn't make sense. The software that back in the day would be in a disk that had "already been in 10 other machines", can now come from a website that serves millions of machines with the same malware infected programs.