You're implicitly assuming that there are only two classes of problems: ones where performance doesn't matter at all, no matter how awful, and ones where one is

You're implicitly assuming that there are only two classes of problems: ones where performance doesn't matter at all, no matter how awful, and ones where one is willing to expend unlimited amounts of wizard-level optimization effort to achieve maximum performance. On the contrary, in practice, it is important that the obvious code a programmer would write should be reasonably efficient (let's say, within an order of magnitude time and space of the optimal single-core solution). For this (very simple problem), this article makes it clear that is not true in Haskell. In contrast I believe it would be true in Rust and even Python (without having written the programs, but using BufReader::lines() and String::split() in Rust and the lines iterator and split() in Python). It's also a problem for Haskell that the first thing you do for performance is to disable one of the key features that distinguishes Haskell from other languages.