Biden can stop it today if he wants, either by withholding weapons or by direct intervention (although an embargo would probably suffice). But the fact that the US is STILL sending weapons is nothing less than direct complicity. People have been shot for less during the Nuremberg Trials.
If the only alternative to the failing status quo is the far right then we are doomed. Keir Starmer is not a beacon of hope, he is a pause button on worse to come.