What are you suggesting? Are you saying the Acacia trees should be smaller or they should spawn less frequently? If you're suggesting either of those, no support. I think the Acacia trees are fine the way they are.
Real life savannas have all different variations of trees, all of different densities. Not all of them are the perfect picturesque landscapes with only one tree for five miles; in fact; some of them have trees more dense than Minecraft.