"But I'm not brilliant, and I don't have a lot of energy, and so I'm also grateful there exists an operating system I can understand, and other people who continue to work to make that operating system useful."
Writing correct, efficient C takes more years to master than people take to learn Rust that I've seen. Also, the C compiler and many other parts of OpenBSD are black boxes to their developers. Your worries apply equally to their situation unless you've read and understood all their dependencies. On top of it, the OpenBSD people are always rewriting stuff for claimed benefits in maintainability or security. It's just when we talk a safe, systems language that can be as simple as a Wirth language or complex as Rust they suddenly can't justify the effort of even piecemeal replacement.
Then, next week, they'll put piles of effort into a mitigation across their toolchain whose benefits are so probabilistic even they can't tell you what attacks will fail or succeed. It's worth it, though, to improve their security standpoint. Unlike the pain of recoding even one utility in something like Rust. That's where this email draws the line.
Of course, I encourage people to do exactly what he asks every time another BS argument is raised. He's worried about drawbacks of a non-C language? Make something like Cyclone or get a Wirth language better at selectively turning off safety compiling to C w/ great C FFI. He's worried about compile times? Fix the compiler. He says utilities aren't rewritten in the better language? Rewrite them showing its advantages esp against the bug reports in OpenBSD's tracker. Just keep pounding away at the problems until he runs out of excuses to import stuff or is extra clear they simply don't like language/method X for arbitrary reasons. Regardless, you get a pile of safe utilities/modules for OpenBSD to do useful things on top of fast, safe tooling. Win, win. :)
Alternatively, contribute those ports to OS's that want to bring in best-of-breed tooling for boosting safety and security. They're usually smaller, less mature, and need all the help they can get.