I suppose that's ultimately in the eye of the beholder. I suspect that if this compiler were to be 10x, 100x bigger, you'd see a pretty big difference. Like rustc, as massive as it is, is pretty legible as compilers go.
But also, the editor plugins don't work on the compiler itself? Why's that? So you can't use Merlin on the OCaml compiler? That doesn't seem great.
And what's with the syntax highlighting being funky? The highlighter appears to think that a lot of these files have unterminated comments or string literals.