That's not actually necessarily true. Even if we adopt this "top possible performance" thing, which isn't how organisms work, you can't guarantee their current set of traits would be this optimal maximum.

Evolution can only work with traits already present, or small additions or deletions. It can't jump around. Meaning, for instance, perhaps a crocodile capable of shooting a literal stream of acid would be even more optimized for this environment - but such a trait can't appear out of thin air, and the necessary stepping stones won't be selected.