iOS isn't just phones anymore
I believe a lot of the changes are taking place because we now have iPhones, iPods, iPads, Apple TV -- iOS in the car and soon iWatch. They had to change things to accommodate all these different devices with different screens and functionality requirements, but yet still try and make them feel familiar.
I loved iOS 6 and was sad to see it go -- especially the polish of it. Not the crazy felt or overboard use of textures such as wood, but the polish of the UI buttons and use of certain apps. I do love iOS 7, but it's not quite there yet. Some UI elements are a vast improvement, some a huge setback. Text over icons is a huge mistake -- just try and look at the weather from the today screen. Trying to delete voicemails often results in a UI text button miss.
That being said, 7.1 fixes some of these issues and I believe iOS 8 will go further, incorporating more icons and dropping some of the text that was a mistake. However, this will also be with a look of having a unified experience between all the different iOS devices.
I agree with the tenant that OS X and iOS should not merge certain things. Look at how Microsoft screwed up Windows 8 trying to make one UI for everything. They completely screwed up the laptop/desktop experience (in terms of market acceptance). Preserving OS X, but taking the two to be more similar (where it makes sense) and interoperable will continue (please Airdrop between devices). But iOS in the car, Apple TV, iWatch/iPhone/iPad/iPod are different devices that will have a similar look and feel. To do that, we had to move beyond iOS 6. As sad as I was to see certain things go, it likely had to be done.
I think they can get the polish back. My biggest frustration with the current state of things is the text label buttons. They're too hard to use trying to touch target areas.