polymorphism isn't simply about alternate implementations. Used carefully, polymorphism creates tiny localized execution contexts that let us work without the need for verbose if-then-else blocks.
While there are cases where it's much more practical to use if-then-else instead of polymorphism, it is more often the case that a more polymorphic coding style will yield a smaller, more readable and less fragile codebase. The number of missed opportunities is a simple count of the if-then-else statements in our code.
