Monads might be simple but it's easy to create confusing large stacks of monad transformers in the haskell world, At least I have found and can often become not

Monads might be simple but it's easy to create confusing large stacks of monad transformers in the haskell world, At least I have found and can often become not the most pleasant to work with aliasing complex monad stacks and all the rest, It can really lose elegance. Some problems beautifully fit as Monads and single monad code can be nice indeed but a few transformers and you can end up with a lot of mess. I do think there is some things that functional programming paradigm struggles with like games programming and other things, I really do think OOP is a better choice for some problems.