Closest I've actually used is Kotlin, but honestly I'd rather use functional paradigms within Java instead.

I've watched a lot of videos on Haskell and Scala, and I think understanding what they are doing and why can only make you a better programmer.

I use the Java functional package all the time. Understanding how to compose functions and define the input type and output type (either of which could be functions) is sort of awakening. Programming by side effect like with a method void doStuffWith(Foo foo) stands out as red flag if you are familiar with FP, but evidently it looks perfectly fine to someone exclusively familiar with OOP.

That all being said, I don't think FP is clearly superior. If you go all in, I suspect you'll find yourself running into familiar problems wrapped in unfamiliar shapes. I think a very happy medium is to define data classes with only getters and setters instead of rich objects. Business logic can then be moved out to some handler, controller, or operand classes that operate on interfaces which the data objects implement.

Mostly, FP forces you to think about some hard things and deliberately implement them instead of seeing what the default behavior is and fighting it when you don't want it.