The problem with many airports is that they're simply not designed for the passenger numbers that use them. Big hub airports are the most guilty of this, and worse still is the piecemeal expansion, adding a terminal here, a new pier there, rolling out a new few taxiways etc. What you end up with is something that alieviates the symptoms a little but will be at capacity within a few short years.

Take terminal 4 at Heathrow, there's a good chance you're going to have to cross an active runway to arrive or leave. Which bright spark thought that would be a good idea?

Gatwick, nice new passenger bridge to take people from the North terminal to the new midfield satelite, forgot to check the tail height of the A380. Now A380 pilots will have to manouever around it because of the 4ft discrepancy.

Any airport with multiple crossing runways, Chicago for instance.

Any airport with parallel runways too close together which stops both runways from being used at the same time, Istanbul for instance.

Airports with massive taxi times to reach the central terminal zone, when whats needed are satelite terminals closer to the runways, DFW and AMS spring to mind.