It's like writing

    fn square(numberToBeSquared : number): number {
      return numberToBeSquared * numberToBeSquared;
    }

The one letter variable version of the function is perfectly readable. Most generics aren't used in a significantly complicated way. Sure, maybe if you're doing something like Haskell's lenses, then you should use descriptive names might be better, but how often are you writing

    type Lens s t a b = forall f. Functor f => (a -> f b) -> s -> f t 

and is

    type Lens source dest gettable settable = 
        forall structure. Functor structure =>
        (gettable -> structure settable) 
        -> source 
        -> structure dest

really any easier to read?