I'm just going by the article this thread is responding to. Perhaps the author's C++ example that he lead with was meant to be a strawman "look how bad C++ is (when we use it this way)"?

If the problem statement is just how to add operators and types to a dynamically typed expression (in some arbitrary language), then in addition to implementing any new operator overloads, there is the question of how to dispatch, which would most obviously be done by mapping (operator, operand type) pairs to the registered type-specific operator implementation (aka overload). Again, not sure what the big deal is here.