There are always those who game the system but you can't do it for an entire career. Army Selection Boards are not perfect but they are the next best thing. I know, I worked there for a while. There are so many checks and balances that no one can be carried or screwed unfairly. Oh, and it's not "ranger tabs," it's Ranger Tab, and it's not given to anyone. It's earned.
"There are so many checks and balances that no one can be carried or screwed unfairly."
If your definition of fairness is limited to "applying the same rules to everyone the same way every time," then that might be true.
However, when the rules are structurally unfair, inequities can emerge despite the equitable application thereof.
Remember what Felix Frankfurter said: There is no greater inequality than the equal treatment of unequals. That is the Catch 22 the bean counters use to displace and dispose of warriors.