Realistically, I don't think that knowing Haskell really would benefit most programmers, especially those working on typical, everyday software systems.

There are some relatively niche situations where it might be a good choice, but those are few and far between.

We've seen the most useful and practical features offered by Haskell make their way into other more mainstream languages over the years. The more theoretical features haven't made this transition because they really aren't all that practical.

At this point, most programmers would be better off learning more about security, cryptography, databases, networking and other everyday topics than they would be by learning about the more theoretical functionality offered by Haskell.