Except that in cases where issues are supra national this helps. Could a local court do it, sure. But in this case enforcement is done by signatory countries within their own borders. This means people wanted cannot travel to any signatory country. Which is not nothing in my book.

And depending on the resolve of a country that has a pending case, a wanted person hiding in a country that is not a signatory, might wake up in the trunk of a car parked in the Hague one day. And the court publicly convicted and jailed several high profile war criminals.

So our definition of useless is different.

Edit: Don't let perfect get in the way of good.