SSDs mitigate those issues but it is so painful to run things on mechanical drives, a lot of which is down to the antivirus processes. The practical realities have changed.
(Also things being snappy and fast I don’t think is a common memory of people when the machines the author is writing about were contemporary. The world of software is much bigger than notepad and cmd.exe)
IIRC Win8's also the first Windows I found unusable on spinning rust. Part of it may have been AV, but things like opening the start menu had significantly worse delays there than on a flash disk. It seems like they'd simply disregarded all development/design discipline about disk I/O, across the OS.
... which, you keep doing that everywhere, lots of devs making lazy choices to just grab this from disk here or just write a little data synchronously there, and it'll add up to non-negligible delay, even on a flash disk. And it'll make an HDD craaaawl. Which is exactly what happened.
Thankfully we’re largely past that.
That said, I rarely see malware on most of the machines I touch. I get more calls about automatically fullscreened browser windows with scare text and a phone number to call than any actual software problems.
Defender does work well enough for any average person and I’m happy if only because the vast majority of AV software is sold in the most disgusting way. Just as bad as the malware scare tactics honestly.
Tools like that are basically hit-and-run and they don't need to stick around to do lasting damage.