[lucasdicioccio]

There is a myth that "monads" are magical insights of some sort -- it's not.

Difficult to understand: likely yes because the myth is not groundless. What "monads" capture is how to combine things with a lot of ceremony: (0) the things that we want to combine are sharing some structure/properies (1) we can inspect the first thing before deciding what the second thing is (2) we can inspect both before deciding what is the resulting combination. What requires a lot of thought is appreciating why "inspect, decide, combine" are unified in a single concept.

Important: indeed, because in Haskell-like languages monads are pervasive and even have syntactic primitives. It's also extremely useful when manipulating concepts or approaching libraries that implement some monadic behaviour (e.g. promises in JS) because the "mental model" is rigorous. If you tell someone a library is a monadic-DSL to express business rules in a specific domain, you're giving them a headstart.

Some final lament: there's a fraction of people who found that disparaging (or over-hyping) the concept was a sure-fire way to yield social gain. Thus, when learning the concept of monads, one situational difficulty that we should not understate is that one has to overcome the peer-pressure from their circle of colleagues/friends. Forging one's understanding and opinions takes more detachment than the typical tech job provides.