Ironically, too much freedom can hurt design. Without the constraint of the complexity meter, newer creators often "spam" parts (like stacking 50 damage spikes) to create overpowering, messy "god creatures." The limit actually forced players to be clever and efficient; without it, designs can sometimes become cluttered.
Despite the popular search term, there isn't a single file called "Unlimited Complexity." Instead, the community has created several mods that achieve the same result. The most famous and widely used is (often found on the SporeMods forums or DavoOnline). Spore Mod Unlimited Complexity
The concept of unlimited complexity in Spore has significant implications for game design, modding, and the gaming industry as a whole: Ironically, too much freedom can hurt design