[lmm]

> From my experience having used Haskell (a long time ago), the main benefit of Monads is the `do` and <- syntax. Once you got your thing to satisfy the Monad interface, you unlocked the nice syntax for writing code.

Nah, I don't even use the syntax much any more. The main benefit is the huge library ecosystem that works generically with any monad, so that if you want to e.g. traverse over a datastructure with your effectful action you can just use cataM or whatnot from recursion-schemes instead of writing it yourself, if you want to compose pipelines of them you just use Conduit, etc.