the only other haskell compiler is MicroHs. and it has no pragmas. it just enables the whole thing.
this is not a real problem in practice. even without the GHC20XX stuff (which is nice). it feels like a problem a novice would point at (and be totally wrong)
sorry your favorite language doesn't let you import language features according to your needs. half of them have trade-offs! like -XOverloadedLists. Useful, but hurts inference. Maybe you don't want it globally. But maybe in a few modules, it's perfect. {-# LANGUAGE OverloadedLists -#} is the answer that no other mainstream lang has.
-XPolyKinds is another great example of that sort of extension.
Preferably there would be more implementation. But if they only implement the "standard" language, it will be missing a lot of things. That is the point!
It's not Haskell anymore. It's Glasgow Haskell. It's its own language at this point.
And those features are not a library that you just throw in, they are compiler specific.