Apple also made mistakes while they let him take the lead for certain things. E.g.:
To be fair: there are for sure also things he did that were good and benefit us all, but it's not a perfect track record at all.
There's plenty of stuff we all bought that is clearly faulty and/or design above functionality and if Jony Ive is to take the credits for the successes, he's also to blame for the failures he created (or led if / where he didn't do it all himself).
If you aks me: Apple is well capable of making mistakes without him as well. But letting him have free reign at Apple for a while was a mistake. To make a well-balanced device you cannot let either engineering nor aesthetics overrule the other. The compromise needs to be made elsewhere.