On one end we have FP, which is great for expressiveness and its declarative nature of getting things done, side-effect free, with nearly perl like terseness :)... but on the opposite end you have von Neumann CPU architectures which know nothing about FP. The utopian "silver bullet" is always something in the middle of course, a language that can give you the power and expressiveness of FP without sacrificing all the things that FP style compels you to bear - like mutability, performance optimizations/fine tuning, etc.

Personally, I find languages like Scala to be right there in the middle, where neither performance nor FP expressiveness is sacrificed severely.

That makes Scala flippin complex like C++ was, but it is probably the best attempt to bridge this gap if we all just want to learn "one language to rule them all" and incorporates both FP and imnperative/mutable style techniques that milk the hardware for what it's worth as well as give you the power/expressiveness of FP.

Of course one can write an operating system in Haskell... just as one can imitate functional style programming in C... or we can come up w/some "middle ground" language that takes the cake from both worlds and call that "the best".

My point is, this quest or journey for the best language/paradigm never ends and always shifts across the years as hardware develops and as we discover better ways of doing more with less (e.g. the crux of FP).

IMHO, ultimately you have to pick an appropriate language (tool) for the job at hand. If we forget that languages/programming paradigms are just tools... then, you'll forgive me for saying, we become tools ourselves. Or... fools, rather.

To me, whomever has realized this trade-off, is a true zen master of programming/engineering...not the one who espouses one paradigm/language over another. That's just me tho... YMMV.