It's got nothing to do with Traveller. It's been like that for a while. Mostly ISC pax as they are most of the population.
Plans for expansion never keep up with the explosive growth. Can't comment on the duty free, as I don't know.
The last time I went thru, we used a stand-off bay with airstairs, bussed to the terminal, entered via the transit lounge (it's called transitting the transit lounge), and yes, the terminal was absolutely jam packed.
I don't think those in govt. use the regular terminal!!! I'm sure over the other side is much more genteel.
When the expansion happens, things will improve, but where they intend to put the planes and people in the mean-time (incl. planned start-ups)?????