For example, OCaml has an object system (the “O”), polymorphic variants (somewhere between ADTs and symbols), parameterised/first-class modules, and named/optional function parameters. A lot of these things have suitable replacements in Haskell, they’re just not in the language directly. And of course, Haskell has plenty of features that OCaml and F# lack, such as pervasive purity, typeclasses, and an array of useful advanced type system features. It’s tradeoffs all the way down. :)