You need to remember that when those ads aired Windows still ran everything as root and had genuine "viruses", not trojans or other malware. But a virus as in the definition of the term. That Macs and Linux had a sane security model really did make them essentially "immune to viruses" in a very real way.

Today, a genuine virus is a rare thing, most malware are trojans. But back then viruses were the dominant form of malware. It's quite unfair to criticize people claiming Macs don't get "viruses" by changing the context on them to include all malware. That's not the claim people made.

Those ads still ran in 2015 on apple.com.

By that time the user restriction model of Vista had existed for 8 years.

Yes, but a decade or more ago. The security landscape and perceptions around it have changed.

Also, back then the difference between MacOS and Windows was pretty stark so this was a valid marketing point. Not that the ads didn't oversell it, of course.

Wrong. They still do:

https://www.apple.com/business/products-platform/

Nothing on that site makes the claim that Apple software is immune from malware. They claim that it's "secure", but that's relative anyways. All of the real iOS malware I know of abuses either jailbroken devices or enterprise provisionings. The standard infection case of "ran something you shouldn't have" or drive by downloading is a lot harder to pull off there.

They still do. https://www.youtube.com/watch?v=dRM31VRNQw0

That's iOS vs. Windows and we were taking about macOS.

I think that marketing language is a bit BS-y, though.

Probably the general idea they are pushing, that iOS is less susceptible to malware than a laptop, is probably true, so it doesn't bother me much.