When you have state...I mean real state, it sure is nice to encapsulate that state in an object rather than in what is basically an unencapsulated monad. OO supports state encapsulation, pure FP basically does not, that is a big deal. Immutable programming sort of side steps the issue, that state is needed at all, that an interactive program can somehow be stateless is ridiculous, even many batch programs require some form of state (even if it is unencapsulated in a monad).
Your 60-line function decomposed into nice small parts using beautiful composable abstractions is an FP pipe dream. Yes, if the problem is well understood, someone has thought about it for a long time and has come up with some beautiful abstraction that works for a narrow set of related problems. Now, as soon as you venture outside of a well-understood/nice abstraction domain, your code is just as bad in FP, if you can figure out how to implement at all.
Your 60-line function decomposed into nice small parts using beautiful composable abstractions is an FP pipe dream. Yes, if the problem is well understood, someone has thought about it for a long time and has come up with some beautiful abstraction that works for a narrow set of related problems. Now, as soon as you venture outside of a well-understood/nice abstraction domain, your code is just as bad in FP, if you can figure out how to implement at all.