To answer it succinctly, I'll use the programming language example that I used.

Let's say that you have never programmed before, so you come to me for help. I start teaching you. The first lesson, I teach you how to output "hello world". The second lesson, I teach you about monads. Honestly, how do you think you'd do?

There isn't anything absolutely wrong about monads, but I'd tend to argue that they're a little too advanced for someone who only knows how to output "hello world". In this example, I'd say that teaching you about monads in the second lesson was inappropriate - you likely won't gain from it, in fact, it's more likely that learning about monads too soon will actually hurt your progress.