Before 2010-something, the very popular meme in software engineering was that functional programming is really hard to understand, and really not suited for anything outside of academia. [1] Now that I've been programming in an immutable functional language for almost a decade (Elixir), I'm certain the meme was mostly born out of unfamiliarity [2] than actual complexity; it's really not that much different than imperative, just requires a different approach and understanding of the trade-offs. Writing a distributed system (say, a web app backend) in an imperative, mutable language in this day and age is increasingly a laughable proposition in my view. Use the right tool for the problem at hand.

Many academically-trained developers never got exposed to FP in school, and to this day you can still hear, albeit in much lesser numbers thanks to the popularity of Elixir/Clojure/etc., the meme of FP being "hard" perpetuated.

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1: I would go so far as to blame Haskell for the misplaced belief that FP means overcomplicated type theory when all you want is a for loop and a mutable data-structure.

2: I played with OCaml 10+ years ago, and couldn't make head or tails of it. I tried again recently, and it just felt familiar and quite obvious.

> the very popular meme in software engineering was that functional programming is really hard

> I'm certain the meme was mostly born out of unfamiliarity

> I would go so far as to blame Haskell for the misplaced belief that FP means overcomplicated type theory