Well, yes and no. In priciple I agree about not reinveting the wheel, but I always personally found the option for GUI modding in MMO's very problematic in the first place. The UI very much defines the whole gaming experience of a game, and changing it can change the fundementals of what the game is actually about. I can see how some mods help make the game better, but many push game balance or game focus to a degree that just destroy the intended game experince.
I find UI modding nearly as problematic as something like P2W. Yeah, I really just said that, but I truely do.