Re: The sorry state of Apple's garbled App Store Update Page: High Sierra.
At the same time, my 2014 MacBook is running Big Sur just fine, and still gets security updates. Heck even the iPhone 6 I still have from that time just got a security update, Not seen hardware supported that long anywhere else.
As for desktop, the only way the Windows TCO lies lower than MacOS is if you omit the waste of the most precious and costly resource of all: staff time (which, naturally, Windows TCO studies do).
Now I'm the first to admit that Apple is regrettably doing less well on the usability front than it used to, but patch, crash and reboot events still clock up enough of a meaningful and financially significant difference. That doesn't count for home use, of course, but at Enterprise level this matter a lot - which is why Windows TCO studies studiously avoid the very mention of the idea.