While I understand what you're saying, I really enjoy what excavation does, and the versatility it provides to finding items that aren't so common. I definitely do not want the list of treasures that excavation provides to be shortened.
I particularly enjoy being able to get cocoa and mushrooms from dirt, this allow me (a veteran mcmmo player) the ability to find food sources significantly easier, when in a pinch. In this case, I could be lost in a mineshaft, dig out a spot of dirt to get mushrooms, and then the wood from the shaft, and I can have mushroom soup; combined with the skeletons(bonemeal) that are already there, I can have a quick mushroom farm on the fly whenever I needed to stop and replenish my food stores, in the case that I can't find my way back, or don't want to head home yet. While it seems somewhat silly for cocoa beans to be dropping from dirt, because of how easy they are to find, they were dropping from dirt long before you could farm them, and they were quite a welcome reward for obtaining excavation at that level.
