The problem with "traditionally functional stuff" was that one could only use functional programming for a subset of problems. Monads allow Haskell programmers

The problem with "traditionally functional stuff" was that one could only use functional programming for a subset of problems. Monads allow Haskell programmers to use FP to solve problems involving IO, mutation and effects. This is not redefining FP, it is extending it to a wider class of problems.