There's a wonderful study (covered in the excellent Made to Stick ) which asks people to tap out a song using a pen on a desk but with no other music. People think that they do a perfect job but the people across the desk have NO idea what they are doing. Ultimately, this comes from the tapper having the song running in their head at the same time they're tapping, and being ineffective at communicating that with just the beat.
On reading this INCREDIBLY harsh commentary of iOS 7, I realize this what the most recent design of the product suffers from. Look at this comparison of the icons:
These icons are NOT GOOD. Well, let me correct that. They're not good ON THEIR OWN. In comparison, or as a riff, on the original icons, they're not bad. Kind of a study on a nice original work. But that's not what you have - you have icons that need to stand on your own - and these just don't. Advice for all product people - be aware of your context and make sure your work can stand solo!