You believe that a meeting of bishops representing less than a quarter of the world’s Orthodox population has automatic authority over the rest? On what basis?
On the basis that the synod was duly and canonically called by the patriarchs and heads of the autocephalous churches. The fact that Putin and his version of the Pre 1917 Holy Synod and their running dog Kirill panicked that Ukraine’s declaration of autocephally might be recognized and so stayed home doesn’t change any of that. As for it being binding on everyone, that’s likely the intention and expectation of the independent hierarchs. The decisions are binding on all hierarchs until such time, if ever, that the People withhold their Great Axios. Those hierarchs who refuse to agree are schismatics.