I think parent was thinking of smart constructors and mixed them up with catamorphisms, which, partly due to the mystique of category theory and how seemingly only smart people get it, can be seen as smart destructors.

The thing to note is that they aren't smart in the same way as smart constructors are.

Catas are just dumb destructors, dumb in the same way as plain vanilla "dumb" constructors.

The catas for lists, Maybe, and Either are respectively, foldr, maybe, either.

There's a body of literature on deriving catas automatically. Look under generics or (older) polytypic programming.