One area commonly overlooked (by defenders, but not by attackers) is identity sync infrastructure. If you harden your AD but don't do this, you are wasting your time.
The most common privileged security gaps that attackers exploit come from sacrificing effective privileged admin security on the altar of operational convenience.
If <that one PAM tool everyone uses> was good enough on its own, then no one in banking would get hacked, because they all use it. Clearly there's more to the story.