Broseph, just because you used simple addons, doesn't mean everyone did or complex ones did not exist. Besides that, you fully missed the point. Minecraft needs a official API thats surrounding a core designed for extention, Wow had that, thats why the addons preformed so well.
That and WoW UI does not do as much as minecraft mods do. As I said the main function of most WoW UI enhancement plugins was to display data in different ways hardly altering a thing in the game (as it was forbidden). Some also delt with provideing alternative ways of using macros in a smooth visual way. So the API is not the only thing keeping the addons light weight. They are light weight becasue that's all they need to be.
I'm just saying it's a bad example. WoW UI plugins are nowhere near as heavy. You could point to something like Gary's Mod and their extensions/ content and I would have given nary a peep.
That being said I haven't played wow in 2 years, I have no idea how much has changed on the custom WoW UI front. But I still don't think I'm wrong.