The one huge advantage DS9 had over the other shows is that it was set in a stable location, and had a stable cast of *non* Starfleet people as main characters. Kira and Odo and Quark and Garak could do stuff that even Worf couldn't get away with. Being located in a single place also meant that areas, species, worlds, etc. could get *massively* spotlighted and developed, because we were going to see them again, week after week. It wasn't going to be like Next Generation, where we meet the Ferengi or Bajorans or Trill one Tuesday evening, and then might not see or hear from them *ever again.* The Cardassians and Bajorans have gotten as much screentime and development on Deep Space 9 as the Romulans have gotten on every Star Trek show, ever. That's cool.
(Contrast to Voyager, which, by it's very premise, constantly travelling at maximum warp away from whatever it encountered last week as it tried to get home, could rarely go in depth on a particular race or culture. Look! It's the Kaizon! Who apparently run a section of the Delta quadrant vastly bigger than the Federation, because after *months* of travelling ten times faster than they can go, and crossing hundreds of light-years a day, we keep running into more of them!)
Also them getting to reuse the same set and dressings over and over, and not have to dress and cast the 'planet of the week' every week, meant more time, focus and money to spend on fleshing out the station and it's crew (and Cardassian history, and Ferengi shenanigans, and Bajoran religion, and other stuff that we still don't know, again, about 'major' races like the Romulans).
It's that reason that I'd like to see more 'stationary' Trek shows, such as a Starfleet Academy-based show. I love me some five-year-missions with a new planet and culture and alien race (that we'll probably never see again) each week, because it can be new and fresh and fun, but, at the same time, I also like the idea of exploring a place, a culture, some characters (and some non-Starfleet characters, who, as you point out, can be quite a bit different than the 'too perfect sometimes' Starfleet officers) more deeply.