Wrong!
Add-ons have the complete power to destroy a game without any abuse or misuse. Exactly as they have in WoW. There are thousands of players who do not understand how to play their class in WoW without add-ons. I am one of them. I was convinced into playing wow by co-workers and so the first thing I did was copy a friends add-on profile and have him show me what to do. When the game gets patched and it breaks my add-ons I have no clue if someone is cursed or if my Fingers of Frost are up and what have you. Add-ons that tell you what to do next after a skill only add to the lack of knowledge in how to properly use your class.
This is detrimental to the game no matter how you spin it. If we end up with shortcut add-ons like decursive for example (I'm sure there are better examples) it's all over. I am absolutely fine with things like UI skins, CD timers, parsers (AKA DPS meters) and non-altering add-ons. The second you throw in shortcut add-ons you break FFXIV. Even if, only for the simple fact that at leas 1/2 the population will be playing with a controller and targeting a shortcut will be nearly impossible.
Shipp actually illustrate my point perfectly with "You claim your GF has healed without any healing addons. This is simply ridiculous. No serious raid healer is not going to have a healing addon." If the game requires a 3rd party add-on in order to fulfill your task then it is broken, end of story.
On top of that comes serious balance issues and the result of inaccurate game balance is Elite mobs with 500k HP and no tactical strategy required to beat them. There is no other way around it besides making everything generic like Blizzard has done. Because the field is so vastly split due to which add-ons are used and by whom that the designers have to compensate with simplicity and numbers e.g. more trash mobs, higher HP and less or no visual clues.
Personally I cannot stand most of the WoW add-ons on my screen. They are designed by amateurs with literally no understanding of aesthetics or visual design and they clutter up your screen so bad that all you see is add-ons and nothing in the game. But, because WoW is such a cluster**** of a game, I have to use them. There is no choice and therefore I am forced to live with an even uglier version of an already ugly game.
Yes, some are great to have and I'm not completely against them as a whole but to say that there is nothing negative about them is absolutely ignorant.