In the wild...
they have become essential to ordinary life during the pandemic
I have yet to see a single Chromebook in the wild. They are still as rare as hen's teeth, here in Germany.
Psychologist Abraham Maslow didn't mention Chromebooks when contriving his hierarchy of needs, and yet they have become essential to ordinary life during the pandemic, with the cheap computing devices being used for homeschooling and remote working. Perhaps in recognition of that, Google has added a bevy of new features that …
I have managed over a thousand Chromebooks for schools. They're really pretty good.
"Against that backdrop, eight years seems almost optimistic."
Quite. Three-four years is about average for REALLY GOOD private school kids. In state schools, I'd give it a year or two! Eight years is a long time.
It's sad, though, that it's taken all this time to realise that the way to secure a user terminal is to stop it being a general purpose OS for the user, run as a limited user, don't allow background services and software installs, and just run things through an interpreted browser. We've finally come back to the unprivileged user interface terminal that I've wanted for decades as a network manager, because that's all a user needs.
And if it's compromised (which I have yet to ever witness!) you get control of... a crappy old Chromebook that accesses everything vital over HTTPS on remote servers anyway, so it can't do very much damage at all.
Loving them. Just wish I could explain to staff that, no, you can't "just install" things on them, I'm not pushing every Chrome extension known to man to them (if it lets you "read all website data", it's simply never going near my network), and no you can't "take control" of them so you can look at every kid's screen all the time and manipulate them remotely (maybe in certain limited circumstances, but modern OS just shouldn't allow that and often don't).
They're great things, but they're great things for schools because someone sat, thought about it, and said "We'll just give a highly controlled browser that allows no other software whatsoever" - because you can turn off the Android features and the Linux developer access, and it's just Chrome. And that's all 99% of people need for most things. Hell, our kids video-edit live in the browser with them.
It doesn't need to be all in the browser. I've put together Linux systems with locked-down Kiosk desktops, and also had no problems at all.
One of those icons is a web browser, but native programs are better where available. Much less bandwidth used, and performs very well on even old slow hardware. Still a locked-down, unprivileged user experience with no way to install programs, or even run anything they haven't been given access to.
Of course it's easier to get started when someone did the work for you, but more difficult when you find you need to do something more than the lowest-common-denominator use-case.