**EDIT: Let me get this out of the way first. I feel like its active is cheap and overly-useful on champions like Fizz. But that's a problem with Fizz himself, not the item.**
Yes, it's an excellent item. Probably more beneficial to mages than any single AD item is to ADCs.
But do any of you *seriously* want ADCs to have better itemization? Do any of you *seriously think that ADCs are lacking in power compared to mages?*
I don't know. It feels like ADCs are...adult bodybuilders, and Mages are teens, and you give the teen a pair of boxing gloves, and the bodybuilders go "WTF teens get all the best equipment, so fking broken, how are we supposed to deal with them now? nerf pls"
Man, that sure was a convoluted metaphor. But you get the idea, right? Mages have superior items like Zhonyas, and yet the game still **entirely revolves around which ADC gets fed, as well as the entire team keeping their ADC alive.** Having a great item like Zhonya's still doesn't alleviate the fact that ADCs always have been and always will be the overwhelmingly superior class.
**If you nerf mage itemization, you will just end up with the game revolving even more around the ADC. Heck, they're already being sent toplane. Do you honestly think people wouldn't start taking them mid again, if their itemization was that much better? Do you honestly want triple-ADC comps? *Honestly?***