I believe a large problem with this game is, as you continue to grow, you increase the amount of gold made. People want new lands/buildings to spend their gold on, which would not only make them stronger, but obtain even MORE gold. I am all in for more lands and buildings, but they should come with an expense like towers. These buildings should not be TOO costly, like hoarfrost, but give a large stat increase with a decrease in plunder gained. Thus, slowing down the ally leaderboards and the buildings will be easier to reach. Sorry for the wall of text! TL;DR: Made new lands/buildings that increase stats, but decrease plunder earned like towers.
Another idea, is to release new buildings for highlands that can only be unlocked after 15 hoarfrosts are unlocked. These buildings would go on our low lands and replace all our small plunder buildings with much stronger buildings that yield us no plunder advantage.