There are a lot of concepts that need to be learned first before monads become simple; namely, functional programming (in general, including the lambda calculus, currying and function composition), and Haskell's type system and how type classes work. All of this stuff needs to be understood at a fairly intuitive level. Add to this that the way much monadic code is often used, and the `do` syntax that supports it, can mislead newcomers into trying to understand monadic code as similar to imperative code. Add also that many of the most common monads, like the State monad, have clever monadic instances involving passing functions around which are beautiful but hardly intuitive to understand. Add further that many monads used in practice are monad transformers, increasing the complexity and opacity further and making production code hard to grok for beginners.
So there are many legitimate reasons why monads are a hard concept. That said, I completely agree that the best way to learn them is to actually try to use them. In fact, I think that the main reason monad tutorials are seen as useless is not because they're poorly written, but because no tutorial can teach you monads a fraction as well as you will learn them by actually using them.
So there are many legitimate reasons why monads are a hard concept. That said, I completely agree that the best way to learn them is to actually try to use them. In fact, I think that the main reason monad tutorials are seen as useless is not because they're poorly written, but because no tutorial can teach you monads a fraction as well as you will learn them by actually using them.