Out of ideas
Focusing on quality might be a sign that they'd produced some half-baked code over the past few years. Or it could be a sign that Cook and co have run out of ideas.
I'm leaning towards the latter, considering they're still pushing animoji as a feature. They have a high profile iOS 12 event watched across the world, and they devoted some of this precious time to 'improvements' to animoji!?
The world needs lots of things, but cartoon animations that I can select by gurning at my phone is really not one of them. It's the kind of feature that I'd expect to be knocked up as an app by a 14 year old in a bedroom, which would go down a storm with 12 year old girls in the playground and get the lone developer bought out for a silly amount of money. But it's really not something that should have any place as a core feature in an OS that is trying to focus on quality and performance after quite a few well publicized problems.