Well it's very obvious that the design concept for the PLD includes "simplicity", which many would say is just the "glass is half full" view.
The problem with making the PLD more "engaging" and more "complex" is that it takes a very important variety out of the tanking role---the simple and straight-forward variety. Like how the BLM is the simple and straight-forward variety of ranged DPS, PLD is the same for tanking. And there's nothing wrong with it.
If you want engaging, satisfying tanking play, pick the Warrior. If you want straight-forward, robust tanking play, pick the PLD. That's just how the two jobs are designed.
Please always remember, PLD is not a boring class. It is just that YOU find it boring because it doesn't fit the play style that you enjoy.