You don’t even have to be mentally competent
Just look at our current commander in chief.
C’mon man... I joined in 1988. I was seventeen and a high school dropout. No diploma and no GED. I had an AQFT of 69, which qualified me for service and just about any job I wanted with exception of the nuclear ratings. I retired twenty years later with a Masters of Business Management. Off topic, during that same time period I knew several kids in Colorado who purposely dropped out of high school and got their GEDs so they could go to college a year early! That loophole was closed in Colorado in the mid-nineties.
You shouldn’t out shine or out smart the Commander in Chief.