Apple's piss-poor quality of software design since he took over would be reason enough for him to be removed. The stagnant nature of the hardware design would be reason #2.
A matter of opinion, without getting into the 'iOS 7 is ****' stuff, the general consensus is that Ive's and iOS's new direction is positive. iOS 7 always was going to have teething problems, it's not easy to completely rewrite a design language for an OS. Personally I think the new direction software is great.
As for hardware, seriously you think there are design problems? The hardware designs Apple are creating is absolutely fantastic; yes they may be evolutionary rather than brand new every year. But still, absolutely gorgeous hardware. Absolutely no complaints here