He's hiding behind Amy.
My favorite time was the Smith & Amy era. I loved his portrayal of the Dr, an old man in a young body, someone weird and childish and silly but ragey and angry and shouty too. At times it did get a little Carry On when he was blushing about River or acting like a 8 year old a bit too hard, but I thought he was the best since Baker.
And I liked the Amy dynamic too. I loved that he was her imaginary friend, that Amy was skittish and all over the place but innocent and not cynical. They felt like good characters for kids to watch, I still think they're the best when it comes to engaging little kids into the show. And when Rory arrived he was actually a well rounded dogsbody, and having a proper functioning couple was a nice change from the girl falling in love with the Dr (even though they messed about with it for a couple of really badly thought out episodes).