So it’s like a court where only law abiding citizens agree to its jurisdiction and all the criminals get away with murder because they never signed a treaty.
And yes, I do agree with your general point: the ICC idea is beautiful. The problem is that the parties to the Rome statute (the real "meat" behind the ICC) has no intention to provide justice to the world, but want to use the ICC as a political weapon, in some cases to prepare for war.
If you intend to do nothing, a center that keeps files on individuals, nothing more, documenting all known human rights abuses, would achieve more.