Objectivism's fundamental flaw is that it is justified by a fictional world rather than the real one, which makes it useless for understanding where we actually live.

The big flaw is that it's justified through a fictional world. It's not justified through reference to the real world. It's not empirical in a way. It's not... Rand herself would say this. She's not writing about things how they are, but how they should be. That idealism just really undermines it as a mechanism to understand where we're actually living.