As a system macOS definitely has some holes in keyboard navigation, as well as a couple corners which are KB-navigable but the way to focus them is not immediately obvious.
On the app level, keyboard navigability depends on the developer. If they take the time to dot their I's and cross their T's it's between decent and great, but if they don't care it'll be bad.
On the app level, keyboard navigability depends on the developer. If they take the time to dot their I's and cross their T's it's between decent and great, but if they don't care it'll be bad.