I know opinions vary, but I really think Moffat did a great job with the dynamic between the Doctor, Amy, Rory, and River. He built his own little world within the greater Doctor Who universe. Once all those things went away, however, I think he had a hard time capturing that magic again. He had to continue with new characters (including the new Doctor), but I don't think he had as clear of an idea of what to do with them.
There is an awkwardness to Series 8. Individually, I think Capaldi and Jenna did a great job, but there's something about them that doesn't quite fit in with the stories being told.