All monadic computation can be accomplished with continuations, which offer a way to thread the monadic bind between sub-programs. But at some point this is equivalent to saying that all continuations can be implemented with machine language... True, but beside the point.
The main purpose of ideas like algebraic effects is to build on a firm understanding of a model of computation. Implementing algebraic effects (whether with call/cc or otherwise) lets one specify a program's behaviour more precisely.
Whether this seems useful or not is probably closely aligned with whether you think static types and purity are useful or not, perhaps.
