Never watched Star Trek but in The Orville, it is explained that you get promoted to the higher job if you have a lot of honor and respect from society
So yeah I don’t see how a corrupt politician could rose to admiral. They should either be military expert that already proven great success at a lower rank or as you said ancient captain.
One day we will probably have an episode one day with all the higher ups to see their struggle when they where younger, like a big battle flash back or something like that, it would be cool
lespea