The fact that Chromium OS has been teetering on the edge of deprecation/merging with Android/Fuchsia for a decade I think has deterred people from building stuff on top of it.
It also seems to have a lot of new code every year for very few new features. It's as if they get every new intern to rewrite a bit of the innards, and then next summer another intern rewrites it again.
OTOH, it was used for multiple container-optimized distros by now:
First CoreOS, which forked into Flatcar Linux (now funded by Microsoft) and Fedora CoreOS (rewrite from Gentoo/ChromeOS base to Fedora base), and Google's Container-Optimized System (used heavily in Google Kubernetes Engine).
A lot of code to do very little user visible changes is the nature of operating systems. Making light of the work who work on chromeos just makes you sound ignorant.
It also seems to have a lot of new code every year for very few new features. It's as if they get every new intern to rewrite a bit of the innards, and then next summer another intern rewrites it again.