But yeah, it did strike me as an unusual amount of command staff on the enterprise too... especially when you watch DS9 and Voyager and almost everyone is an ensign or a lieutenant.

I chauk it up to the Enterprise being the flagship - Everyone wants to be there, participating in the big missions. Even when they tried to promote Riker to Captain and give him his own ship several times, he was just like "no, I'm good, thanks." Very different from most modern military practices, but not a bad way to run a military fleet of starships, I suppose.

One of the reasons I liked DS9 so much was that it showed the less glamorous side of being in starfleet. The characters there were mostly low-ranking and were stuck on a remote assignment on a crappy, decades-old station that used to house slaves and refineries with a pretty impossible mission: get this war-torn planet ready to join the Federation. Soon. Even the starfleet officers with occasional parts are low-ranking - we don't even see a starship captain (other than Picard) until the end of season two. Otherwise it's just ensigns & junior grade lieutenants trying to fix whatever mess they've come across.