I don't think Maxis even exists as separate entity anymore. Aren't they just a small division within EA now? EA kept the brand name because Maxis used to be good, but it doesn't mean anything today.
Maxis has a separate studio in Emeryville (by Berkeley), where Spore and SimCity were developed. Maxis isn't exactly small, since The Sims franchise has been responsible for a large share of their profits: A few years ago EA reorganized into three parts, and The Sims division was one of them, but I don't know how they're organized now.
Maxis is no longer comprised of the people or direction that made the company once known as "Maxis", it is an EA subsidiary and run as such.
People assume (with good reason) that the design choices that made Sim City a poor game were made with the publisher's interest placed above the player's.
The lead designers and artists who developed the latest version of SimCity were old time Maxis people, but they've left since it launched. They weren't very happy with what Origin forced them to do with their game.
I think it has more to do with the fact that Maxxis made a good Sim City in the past and now it sucks.