Overloading is dispatching based on types of multiple arguments. If someone adds a more specialized overload, it will be called instead of the existing. The problem is dispatching on polymorphic types. As long as you still have your Squares and Circles intact, the right function will be called. And in C++, keeping the concrete types intact as far as possible is a solid strategy.

For your collection example, at some point you need to introduce some kind of polymorphism to get back to concrete types; but once you're back, overloading works just fine again. The best strategy to recover types depends too much on specifics to be formalized.