The point about how difficult it is to learn is well made and well taken. This difficulty is very contextual though - this is a problem for the language in term

The point about how difficult it is to learn is well made and well taken. This difficulty is very contextual though - this is a problem for the language in terms of adoption, but it's not a problem if, for instance, you're a team of experienced Haskell programmers deciding on which language to use for your Important Business Applications. I think that you overstate the cognitive overhead of reading polymorphic type signatures to those who are reasonably familiar with common idioms. Taking a second to remember that `Maybe a` is a semigroup if its argument is seems like a small cost to pay to me. I think there's a significant benefit to highly polymorphic functions in the standard library which seems to rarely be brought up. Polymorphic functions are applicable more often. So then if the function is already written for you, and you use it, then anyone who reads your code has to look at one less definition to understand it (if they're familiar with the library function). This forms a larger common vocabulary and in some ways imposes a smaller cognitive overhead on the reader. Speaking more broadly, people are often frustrated by the number of abstractions from the standard library that they have to learn to be productive. But they don't notice all of the abstractions they now don't have to learn in individual codebases - because they don't have to exist. And this effect adds up - every time there would have been a slightly less well implemented, proprietary, monomorphic version of a function in a codebase and you use the polymorphic standard library one instead, everyone who reads that code has one less thing to get their head around. It pays for itself. I also feel like you understate the benefits - the amount of times I think for 20 seconds and realize that the complicated function I was about to write is just like, `traverse` or something is incredible to me. I think it's possible to to have legitimate disagreements here, which are often driven by differing personal experiences, and by the kinds of domains people are operating in and so on. I don't think there's a one size fits all answer.