There is lot to do as a tank. People saying they can't do anything to influence the battle are just super lazy. It would be like saying blm is boring because all you have to do is spam fire until oom then spam blizzard then repeat. That's one way to play it, but far from optimal.

Well guess what, same is true for tanks. If you just spam 123 or flash and do nothing else, you are doing it wrong. Warriors get 2 buffs to keep up with 2 low enmity generating combos. Pld can use a crapload of stoneskin and riot blades to get some mana back You can also use flash for the blind debuff. Once you have a comfortable lead in enmity, you should always look into what utility you can bring to the party. For challenging content, there is alot to do as a tank. For nonchallenging content, well guess what, it's the same as a dps, if you don't do good dps, who cares ? 123 all the way too bro. Also if the thing you are doing is not challenging enough, make it challenging. If you never have to use a CD or stoneskin for a given encounter as pld, why not go with one healer instead of two and cover for the lack of second healer through your good use of your abilities ? Yeah, that is noticeable.

tl;dr: if you find tank boring, you are probably playing it wrong. The problem is pretty much the interface between the chair and the keyboard, as often.