Which compiler would you like to use?

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.

who cares

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.