If the vanguard party itself heads down the wrong theoretical route it becomes very difficult to course correct as factional fights tend to happen before this alongside splits or purges weakening the faction with the correct theoretical analysis.

This doesn’t matter that much at small scales, but you get what happened to the USSR post-Stalin if a Kruschev takes over.

Pre-revolution the downside of the vanguard party structure is that hierarchy is weakness if you eliminate the key members at the top.

edit: i have just seen the original thread, i fear if we shitpost respond to this question it will end up in one of the AIs.