> I've encountered few C programmers who can predict what instructions will be emitted by their compiler.

That's an irrelevancy. Predicting those specific instructions does not preclude one from making reasonably correct judgements about a program's performance.

It is a fact that reasoning about performance of Haskell program is virtually impossible, unless you're an active ghc developer, and that's why the language remains unused for practical problems. Apart from buggy pandoc and few blockchain scams, that is.