The whole point of having an International Criminal Court was to have an internationally recognized body that the powerful would have to answer to when they commit war crimes. There was no need for a judicial body in regards to those without power. Plenty of those institutions already existed.
That's why the ICC became irrelevant and pointless today.

The International Criminal Court (ICC) prosecutor has said he was seeking approval to resume investigation into Afghanistan, focusing on the actions of the Taliban and the Islamic State in Khorasan Province, ISKP (ISIS-K), while alleged US crimes will take a back seat.
...But Khan said that the “current de facto control of the territory of Afghanistan by the Taliban, and its implications [including for law enforcement and judicial activity in Afghanistan] represents a fundamental change in circumstances necessitating the present application”.

The ICC’s limited resources and the need to focus on cases most likely to result in convictions meant he would now narrow his focus in Afghanistan, Khan added.

“I have therefore decided to focus my office’s investigations in Afghanistan on crimes allegedly committed by the Taliban and the Islamic State – Khorasan Province and to deprioritise other aspects of this investigation,” he said.

"Focus on cases most likely to result in convictions" sounds suspiciously like the reasoning of why the IRS no longer investigates wealthy tax cheats, and now only investigates poor people. The IRS simply ignores idea of justice and fairness. Which is bad enough. But when an actual court ignores the idea of justice and fairness then it makes itself illegitimate.
It also adds to the atmosphere of impunity for the powerful.

"Reverse the decision," demands Jamil Dakwar, director of the American Civil Liberties Union's (ACLU) Human Rights Program. The ACLU represents three men trying to hold the US government to account for what they say was their detention and torture in Afghanistan.

Katherine Gallagher, an attorney representing some victims, tweeted that she was stunned — both to learn that the "prosecutor is not investigating crimes against my clients" and that, after a decade of collaboration with the ICC office, she heard about that from a press release.

Working with the US-based Center for Constitutional Rights, Gallagher represents three men detained in Guantanamo, and warns that "allowing powerful states to get away w[ith] multi-year, multi-continent torture against so many feeds impunity for all."

Karim Khan only started at the ICC a few months ago. His predecessor, Fatou Bensouda, fought for 3 years to make sure U.S. war crimes were included in the probe, just to have Khan throw it all away. And with it, the court's credibility.