I don't think that tanking is boring at all, and I don't think that "just make staying alive and/or keeping aggro harder" is the answer for people who dislike tanking. In fact, I would argue that people who think this are simply missing the point.

I probably do more tanking than anything else because I have fun with it. I enjoy pulling packs of mobs, bringing them together, and burning them down. I enjoy having the enemy's attention while mitigating damage and dishing out as much as I can. That doesn't mean I want my role to be nothing more than a meatshield for the party. I don't want the expectation to be "just stay alive and take all the damage." I like the expectations as they are now - Get in there, face them head on, and dish out as much damage as you can without failing the basic responsibilities of staying alive and keeping hate.

Could tank classes benefit from more complex rotations? Maybe, if it's done in a way that doesn't significantly increase the risk of tunnel vision. I wouldn't want a tank that plays like a bard, for example, because tanks already have enough stuff to keep an eye on as it is. Generally, though, I believe that the "tank rotation is too simple" complaint is a bit overblown (with the exception of Warrior). I've played nearly every class at max level and the DPS rotations are generally not that much more complicated, and that doesn't even take into consideration all the other things tanks have to deal with such as positioning, enmity, mitigation, and general raid awareness.

Overall, for me, the role that is most relaxing and chill is DPS, not tank. When I play DPS, I can just relax and hang out and focus on hitting my rotation to do damage. Tanking is a role of responsibility and one that demands a lot from the player whereas DPS is just "hit these buttons in this order and pay the minimum amount of attention required to ensure you don't mess up mechanics".