This is the end of official updates for them, they’re not bricked.
Older Chromebooks do have a shitty support lifecycle, it can’t be denied. Newer (post 2020 launch) Chromebooks come with at least 8 years of updates, although that’s from product launch, not from when you buy them. That is comparable to Apple’s support lifecycle.
It is possible to install ChromeOS Flex on out-of-support Chromebooks, though likely you will lose some features. You can also install generic Linux on them, but it’s got to be said it’s a slightly annoying experience.