It’s the mechanical gaps in Marxist philosophy which arguably led to Leninist revisionism in that first era.
The annoying part is that there is now like 100 year of post-Lenin philosophy which MLs love to ignore because the thing they actually care about is relitigating 100 year old geopolitics.
It’s just hopelessly modernist and fails in all the same ways every modernist philosophy of that era does. That’s why it’s annoying why MLs try to lecture you like they know political science - because they clearly have some pretty massive polisci 101 blind spots.