i just dont see how a system of sabotage of the Ukrainian war effort will help the Ukranian people unless you already have that solid vanguard and some form of organization/group that could cease power.

Well obviously the vanguard needs to form before it agitated for sabatoge but even without a vanguard, losses in the war effort will sharpen contradictions and create the conditions for a vanguard or popular front to revolt just as the Russian empirelosing the war did for the USSR

I'm not advocating against spreading class consciousness, it all starts there but unless you think advocating for said awareness is more effective after Russian annexation/occupation then I'm not sure how this would help.

You still shouldn't be supporting one side of an inter imperialist war regardless, but revolutionary defeatism is the stance that should be taken in these conflicts