I disagree, speaking from a standpoint using wow as an example as you did. Add ons are not obligatory, do people use them? Yes. Do they in some cases make certain aspects of the game less stressful/easier to certain players? Yes, thats what they are for. Add ons are not meant to influence the game, or grant an unfair advantage over anyone else(those that do are usually quickly shot down). The primary purpose of add ons is for customization, to make the game better suit your personal playstyle, customizing controls, gathering and displaying information in forms that is more understanding/visibly appealing to you.
I help coordinate raids in wow even still, 2 nights a week. The only addons I use are a UI customization addon for my bars, a dps meter to monitor My damage during boss fights, and omen threat meter, since as a warrior there, I have high initial burst and sustained dps, so do tend to pull off the tanks, and I used to tank, and still do when our offtank is MIA.
All the wow nonsense aside, I would like to see add ons, primarily for the purpose of building a better UI, as I can barely tolerate the in game one now. And ofcourse I want my 2 simple meters to gather information. I could do without a dps meter if we had a in game combat log that I could gather a parse from, but we do not. However a threat meter, for me, is still something I don't like to be without. Especially with such a high influx of new MMOers who haven't yet learned the concept of, Let the tank get aggro before you go crazy.