I think he’s saying like Ledger people bitched about his casting and then surprised everyone by absolutely killing the role.
The only problem is that not everyone devotes themselves to a role like Ledger did. Also not everyone had the quality of writing Ledger had in TDK. The universe doesn’t align itself in such a manner that often.
I hope this doesn’t lead to a fifteen-page debate about the Nolan Batman films. 😉