Arguably ATL is the most efficient airport ammongst AOS (airports of size)..
I always question to what extent that was pure luck. Did they realize back in the 70s that the then common spoke system has issues? Or were they just trying to fit it in the space so went the T-A-B-C-D linear setup? Do not know.
45 years later the only thing they really missed was the huge expansion in international flight. Back in the 70s, ATL international was "regional". True long haul was via the international gateways, not ATL. Even so, the international expansion has gone well, other than the groundside I<>D that sucks.