I don't find Ive's UI design changes "careless". I find them stupid. The guy should be FIRED, IMO. Whatever value he had under Steve Jobs, he's gone ego-mad under Cook. Whatever Cook is good at, it's NOT getting under the hood in any kind of way (where Jobs excelled was either coming up with or at least picking out the best ideas). Honestly, I'm not sure WHAT Tim does. He even hands off most of the presentations to other people. He strikes me more of a middle manager than a CEO for some reason. Apple needs a LEADER not a quiet guy hiding in the background. Ive THINKS he's a leader, but it's clear to me he's someone that has to be reigned in to produce usable output.
Now I don't know whether things like that search box with almost identical grey upon grey contrast was Ive's doing or a design member's doing, but Ive is responsible for APPROVING it. Someone isn't doing their job. Even if I don't agree with the overall new "look" of Yosemite, it shouldn't have glaring readability and usability issues which changes like that create for the user. That SAD thing is they are simple to fix. Change the damn color! It isn't rocket science. I almost feel color blind looking at Yosemite in places.