Nature Structures

No, summoning (as a skill) is a useful thing. You just need to learn how to use it... not even learn, but get used to it, understand it. For example, Charm in Haven is much worse, in my opinion. Nature has an additional chance to increase its army; why would you refuse that? It's obvious that you need to develop it to its full potential. But at least the increase is continuous. With Charm, you might get something here, something there, but there's usually no room in the army for "creatures." Their presence can even lower morale. But Nature summons its own. And replenishment is needed. Especially if you're playing against Necropolis and Stronghold.