However, history has shown

i think that this is the key part. i'm unaware of a leftist victory in the global north since the great depression and i suspect it's because the hegemonic powers have gotten so good and so organized at mitigating possible class cohesion that we're stuck in this pattern until something very drastic happens to society centuries/millennia from now; making a leftist victory a practical impossibility for any of us in ours or the next several generation's lifetimes.