These days it's very common for more than half your work to take place in a browser, with many browser windows, each having many tabs
Every window of the browser almost is like its own application for the user, yet they're all from the same application with the same name for the OS
How does an application switching interface, rather than window switching interface, work out for that, if a lot of what you want to switch between is different windows of the same browser?
(and what if in addition there would be also many terminal emulator windows, each also with many tabs, and maybe some code editors, spread across multiple virtual desktops)
Personally, I think it goes back to early Windows originally supporting very low resolution graphics cards where you simply couldn't display more than a single widow's worth of content at once.
Remember that EGA was only 640×350. You had to have a user interaction method that worked at such a low resolution.
Having things optimised for drag and drop between multiple windows is the reason for Classic Mac OS to only maximize a window enough so that the entire contents of the window is visible, instead of taking up the whole screen.
[0] https://www.folklore.org/StoryView.py?story=Switcher.txt
You're both being silly, but the author is being especially silly to evaluate an operating system mostly based on how he feels about the user interface.
macOS is more than just a user interface, more on that in a bit. That being said, there is no Universe where any Linux user interface nor any user interface developed by Microsoft is superior to Apple's Aqua. Sure, Aqua sucks, but nothing, anywhere, approaches its ease of use (developed for everyone, not just the nitpicky self-proclaimed power users with weird tastes), and the feeling of solidity, like windows, menus and icons have some gravity and aren't just weightless and flat sprites ready to fly off the screen or fail to interact with other graphic elements properly. Frankly, every gui ever has been chasing Apple's guis since 1984. Truth hurts, I'm sure, but those are the facts. NT4 and 2K, very similar, were collectively the best guis Microsoft ever released, and gui-wise, everything since has been an absolute disaster, visually and with interaction, XP and 7 included, just absolute crappy junk of guis, and 10 and 11 are no better. In Linux, I always liked every gui I saw, Gnome and KDE, and really it can be tailored to whatever the user's desire is, can even run WindowMaker for the NeXT feel. But therein lies the problem, no consistency whatsoever and it's not for everyone; it is only for the tinkerers, coders, and Linux admins.
Back to the operating system. macOS is rarely given the credit it deserves for being such a solid stable gui running on top of SUS UNIX. Come' on, the author merely mentions this and says nothing about it, but right there is nearly everything that matters: more software available than any other platform ever plus all the best professional apps (printing, photography, audio, video, etc.) run better on macOS, and massive security benefits right out of the box, default config, but of course it can also be hardened, trivially, and then pretty much forgotten. You can never forget to attend to the security of your Windows machines, update, upgrade, constant, ceaseless, never ending scans, but that is in addition to its catastrophe of a user interface, so there's that.
[1] https://www.businessinsider.com/how-to-switch-between-window...