Jony Ive was perfect for Apple as long as his instincts were counterbalanced by Steve Jobs' consumer-focused intuition (which on occasion resulted in the reworking of a rather severe Ive design into something friendlier and more useful). Once Ive started running the design show without that pushback, Apple's efforts became more hit-and-miss: the incredibly good Apple Watch design on one hand; some arguably functionality-compromised computer efforts on the other hand.
In my opinion, Apple needs a chief designer who is as talented and opinionated as Ive, but it also needs that strong counterbalance, which we have to hope Jeff Williams can provide.