Wokka wokka!

I’ve seen a lot of stuff about how lightning-bending is not as special as it used to be. Does it not make sense that the population of the world is a whole lot bigger than the Fire Nation army, and therefor, there are a lot more benders of any ilk than we have seen before?
While Republic City is not the entire Avatar world, it is arguably the biggest city and would bring benders of all sorts from around the world, like lightning or metal-benders, or even healers?