That's the PR line, but only describes about 5% of the problem with haskell.
But haskell's not relatively unpopular because it was late to add things like linear types. It's relatively unpopular because it doesn't care much about user experience.
Consider: it's getting linear types before an efficient string type in `base`. The first goal of this language is not good engineering practices and getting things right. The first goal of this language is "cool type stuff", with good engineering maybe goal 10 or something (is O(n^2) `nub` ever going to be deprecated I wonder?). And that's fine, we need a language for cool type stuff, let's just be honest about it.
Context: I've been Haskelling for 5 years, I've written a fair amount of FOSS in it, and it's my favorite language. I just want to help spread an honest impression of it.