They are my daily bread and I sloppily lumped them in with "web [...] services", but in hindsight they ought to be a separate category - fundamentally about a different layer,infrastructure, and might not even be networked.
Many tools on DevOps ecosystem are now going through the RIIR phenomenon, and I bet, had Rust 1.0 been available when Kubernetes decided to migrate away from Java, after Go heads joined the team (see FOSDEM talk on the matter), or Docker moving away from Python, most of those tools would have been written in Rust instead.
The Rust of today wouldn't be chosen over the Go of a decade ago, it is fundamentally a bad fit, for similar reasons that the already mature C++ wasn't. Java (similar to C#) would've been viable mainly due to maturity and ecosystem effects, Kotlin/Native might be a contender in another half decade, sooner if the team were to shift priorities.
I say this not just for Kubernetes etc., but greenfield projects today as well.
Let's just entertain the idea and pretend that this is a notable project and that one would count it as DevOps tooling.
Here are the top 10 across the CNCF in terms of size, courtesy of GitHub's API: