There is greater leverage with Haskell in tackling hard problems or problems where there are existing quality libraries that can be leveraged (such as parsing).

There is greater leverage with Haskell in tackling hard problems or problems where there are existing quality libraries that can be leveraged (such as parsing). Haskell is probably not a good choice in comparison to C/Go/Java if having the best possible CPU performance is a requirement. I am not sure what you mean by a server backend, but that could potentially describe most Haskell code written in the modern networked world. I think the idea though that one language is objectively better at a certain task gets strongly warped by subjective factors. Ultimately language decision is more about the team of programmers you have, the available libraries and ecosystems, and the team's understanding of it. Perhaps not surprisingly, we have found that for programmers already experienced in Haskell, Haskell is a great language for most problems.