I'd say that it's one take on that paradigm, the Way of Monads is not the only way to do purely functional, Clean uses uniqueness typing instead. Though it otherwise has rather similar properties to Haskell.
Monad itself is never a silver bullet. Type systems and Composability are the true power of FP IMO.
This is no reason to avoid arguably the most popular (and state-of-the-art) function language and implementation out there.
Space leaks I'd like to read more about but writings about them are a bit hard to come by. Recommendations?