Branching off of OverloadedStringDefault proposal:
After thinking about it for a bit:

The only real
Foldable
/Traversable
instances I can count inbase
areList
andArray
. Every other one is there to either extract 01 elements or tocoerce
away a newtype. 
Data structure modules tend to be imported qualified, as their exports clash with
Prelude
.Map.foldr
is as good asfoldr
in my mind, as these functions are used sparsely. 
Data structures do not need all of the functions:

foldl
/foldr'
forList
are the classic example, indeed not all datatypes are born symmetric;  For nonempty types
null
is alwaysFalse
andtoList
has one or more elements guaranteed; 
elem
/maximum
/minimum
/sum
/product
areList
processing functions and there is no expectation for other datatypes to implement any of them; 
foldMap'
is a complete mystery to me (isnât it always a strict fold around a monoidal accumulator?).


Monomorphic / indexed / existential / higherkinded stuff does not fit these definitions and thus either chooses to go the simple way or branches out into a whole extended bridgeburning universe that suffers from the exact same issues.
The ideas around Foldable
/ Traversable
and their extensions are solid, and libraries should be encouraged to share them. Explanations of terminology and mathematical reasoning should be documented somewhere easily accessible, but typeclasses are not a good tool here.
And yes, I know, even if most of the community fervently agrees with this, these typeclasses will not be dismantled overnight. If base5
were to be agreed upon, I could see this be one of the changes.