But I'd love to try! Maybe I'll take an online class for fun.
And algebraic data types make it possible to make your code conform to reality in ways that classes can't. Once you're exposed to them, it's very much like learning about addition after having been able to multiply for your whole life. (In fact that's more than a metaphor -- it's what's happening, in a category theoretic sense.)
Haskell has other cool stuff too -- lenses, effect systems, recursion schemes, searching for functions based on their type signatures, really it's a very long list -- but I think laziness, purity and ADTs are the ones that really changed my brain for the better.
Your comment is great though, consider me convinced. I've done a bit of messing with Lisp, but really would like to try write something in Haskell, or slog through a book or two, some day.
I felt the same way, a lot of people feel that way.
This is in part because FP is difficult, typed FP is difficult, and Haskell is difficult. All by themselves. They do get easier once you intuit more and more FP in general I'd say.
Then there's also a phenomena described in the Haskell Pyramid[0] where it sometimes appears more difficult than it really is.
Like a lot of things, actually building something gets you a long way, esp. with the advent of chat AIs as it's comparatively easy to go back an fourth and learn little by little.
This impression can be changed somehow by the fact that Haskell and its community has two faces: There is the friendly, "stuff-just-works" and "oh-nice-look-at-these-easy-to-understand-and-usefull-abstractions" pragmatic Haskell that uses the vanilla Language without many extensions, and being written by people that solve some real-world problem by programming.
Then there is the hardcore academic crowd - in my experience, very friendly, but heavily into mathematics, types and program language theory. They make use of the fact that Haskell is also a research language with many extensions that are someones PhD thesis. Which might also be the only documentation for that particular extension if you are unlucky. However, you can always ask - the community is rather on the side of oversharing information than the opposite.
Rust fills that gaping hole in my heart that Haskell opened a bit - not completely, but when it comes to $dayjob type of work, it feels somewhat similar (fight the compiler, but "when it compiles, it runs").