Monolithic kernels don't "focus on correctness". Some people might when writing one, plan 9 for example. But plenty don't, like linux as the most obvious example.
Reading the Plan 9 kernel code hasn't convinced me that its authors focused on correctness. The kernel code is pretty, and its twenty-year-old architecture could pass as only ten years old; but even excluding drivers, there is no shortage of bugs.
You found lots of bugs reading the plan 9 kernel source, and forgot to report them?
Interestingly, important parts of the Linux kernel are proven correct (e.g. the scheduler). But yeah...not the whole thing.
What? When and where has any part of linux been proven correct?
What I mean is that they try to achieve stability by eliminating bugs, not by doing damage control. Proactive vs reactive.
And what I mean is that is simply not true. Monolithic kernels give us unstable systems like windows, linux, BSDs, etc. Virtually ever highly reliable operating system is built on a microkernel.