You can study programming languages themselves without misusing C++ features in horrible ways. Monads are already overused and misunderstood- using them in C++ templates just makes things worse.
Where are they overused?
This trend originated with Haskell and then when people who learned monads without understanding the other (often better) abstractions spread them everywhere else, we got things like this article.
Using monads, especially in a language like C++ templates or Scala, but also in Haskell, can overcomplicate things and make things longer than if you just solved the problem the direct way.
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As an example of where monads are overused, look at the Maybe/Option type. I've read several articles that advocate using bind and/or Haskell's do-notation to move a string of null checks out of the main program.
This is great, but it's much more easily and expressively done with applicative functors. Instead of assigning all the intermediate results to names, you can just do
someFunction <$> Just 3 <*> Just "Something"
and it looks like regular function application. Because Applicative is a more general interface that Monad, it also has the plus of working with more types.
I think the Maybe example may be wrong, though. You may need the power of Monads sometimes. If you have a function that requires the result of a different function which was wrapped in Maybe, Applicative will not be enough.
Example:
xmlChild :: String -> Element -> Maybe Element
myPath = xmlChild "a" >=> xmlChild "b" >=> xmlChild "c"