After the 2000s, the US began increasingly limiting those with ethnic or potential familial ties from working beats related to those countries. A Chinese American wouldn't pass the security clearance muster for the China role, nor a Jewish American for an Israel role.
There were attempts to potentially remediate this during the Biden admin, but it fell to the wayside [0][1]
Some white dude who went to high school in White Plains and college at Tufts just isn't going to have the domain or cultural experience or knowledge needed to really understand China or Iran, and it legitimately has caused a lot of IR Policy to become divorced from reality.
[0] - https://www.politico.com/news/2021/03/16/state-department-di...
[1] - https://www.politico.com/news/2021/03/18/asian-americans-sta...