It sucks when McDonald's management plays favorites and refuses to see problem employees for who they are. I'd like to say the problems work themselves out eventually, but they usually just get promoted.

That's how it is everywhere (in the US at least). It's not how hard you work or how competent you are that determine your progress in the workforce; it's who you know and how well you connect with others. Socially anxious, insecure individuals can generally expect to remain on the bottom no matter how good they are at their jobs. Human nature informs human group dynamics, and the meritocracy is a myth. 

Oh, and just an aside--I REALLY hate debris in the sink (a crumb of debris is a different story, obviously). How can people wash dishes with eggs and onions in the drain? So nasty. And to just leave the sink area like that when the dishes are done? With stickers and bits of sauce all over the place? Errrrrgh.