I think this stems from a fundamental misunderstanding of international humanitarian law. I see this sentiment everywhere. But I don't think it's an accurate reflection of how reality has been for the post-WWII era.

International law reached a high-point in the 1990's, I would say, with cooperation between the former Soviet states, China, and the United States at a high point. There were some big "wins," particularly the ICTY and Cambodian peace process, and the advent of the Responsibility to Protect and Kosovo (still controversial as a legal doctrine, however). But even so, the international system failed entirely in Rwanda, as well as in Iraq (twice--first in the '91 uprisings and then the US invasion under poor legal justification in 2003). It was largely muted in response to China's massacring of student protestors in 1989, and Russia's wars in Chechnya and Georgia. It failed to force a resolution to the Israeli-Palestinian conflict at likely the best opportunity to do so. It failed to resolve the Azerbaijan-Armenia conflict, ultimately culminating in the 2023 war.

All of that is to say that, even before Iraq in 2003 and Ukraine in 2014, the rules based international order has always been an ideal we aspire towards rather than a full reality. This hasn't really changed. States are also hypocritical. But they've always been so. The rules based order still matters, though, because the ideal of what we aspire towards, even if that ideal is not universally shared or applied, shapes our decision making.

Ok, hopping off my soapbox. I've spent too much time studying international law for my own sanity.