If you're a computer programmer, coding in a high level language with closures and garbage collections, and you are confused by flatMap: I think you should find another career.

We need to have a basic level of competency.

I don't think anyone is confused by flatMap in isolation. It's chains of not-very-obvious data transformations. When I have to do one of these I typically break out each step into it's own line/block and add comments with an example object to show precisely what every intermediate step looks like. They're hard to follow otherwise.

And functional programming snorts these long chains like lines of coke and when you add some random curried functions and people who write in a pointless^H point-free style it's easier than folks like to admit it to end up with write-only code.

I've never found myself with a block of code that could be expressed as a flatMap and thought it would be easier to understand by expressing it as such. I'm perfectly capable of writing functional code but after reading it back I almost always throw it out for something imperative because it's clearer as to what's really going on. The code is going to be executed in an order at the end of the day, why make it harder to see what it will be?